Random impact FEM simulation of irregularly-shaped media for parametric study of vibratory surface enhancement

2021 ◽  
pp. 095440542199012
Author(s):  
Jing Zhang ◽  
Joselito Yam Alcaraz ◽  
Swee-Hock Yeo ◽  
Arun Prasanth Nagalingam ◽  
Abhay Gopinath
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Parametric Study ◽  
Thermal Loading ◽  
Low Cycle Fatigue ◽  
Fem Simulation ◽  
Surface Finishing ◽  
Aerospace Materials ◽  
Surface Enhancement ◽  
Steel Balls

Aerospace materials experience high levels of mechanical and thermal loading, high/low cycle fatigue, and damage from foreign objects during service, which can lead to premature retirement. Mechanical surface treatments of metallic components, for example, fan blades and blisks, are proven to improve fatigue life, improve wear resistance and avoid stress corrosion by introducing work hardening, compressive residual stresses of sub-surface, and surface finishing. Vibropeening can enhance aerospace materials’ fatigue life involving the kinetic agitation of hardened steel media in a vibratory finishing machine that induces compressive stresses into the component sub-layers while keeping a finished surface. Spherical steel balls are the most widely used shape among steel-based media and have been explored for decades. However, they are not always versatile, which cannot access deep grooves, sharp corners, and intricate profiles. Steel ballcones or satellites, when mixed with round steel balls and other steel media (diagonals, pins, eclipses, cones), works very well in such areas that ball-shaped media are unable to reach. However, a methodology of study the effect of irregularly-shaped media in surface enhancement processes has not been established. This paper proposes a finite element-based model to present a methodology for the parametric study of vibratory surface enhancement with irregularly-shaped media and investigates residual stress profiles within a treated area of an Inconel component. The methodology is discussed in detail, which involves a stochastic simulation of orientation, impact force, and impact location. The contrasting effects of a high aspect ratio, or an edge contact, as opposed to rounded and oblique contacts are demonstrated, with further analysis on the superposition of these effects. Finally, the simulation results are compared with actual residual stress measurements and was found to have a max percent difference of 34% up to 20 [Formula: see text]m below the media surface.

Crack Non-Circularity and Finite Erosion Effects on the 3D SIFs of a Bauschinger Modified Pressurized Thick-Walled Cylinder

2015 ◽  
Author(s):  
Qin Ma ◽  
Cesar Levy ◽  
Mordechai Perl
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Numerical Analysis ◽  
Material Properties ◽  
Thermal Loading ◽  
Circular Crack ◽  
Finite Element Package ◽  
Pressurized Cylinder ◽  
Walled Cylinder

Our previous studies have demonstrated that the 3D SIFs of a pressurized cylinder can be greatly affected by many factors. While an autofrettage process may introduce favorable residual stresses at the bore of the cylinder, other factors such as erosions and cracks, once introduced, may greatly reduce the effectiveness of the autofrettage results. In this study, we focus on how the non-circularity of cracks affects the 3D SIFs for a cylinder that contains finite erosions while keeping other conditions and material properties unchanged. Numerical analysis was performed using ANSYS, a standard commercially available finite element package. The residual stress due to any autofrettage process was simulated using the equivalent thermal loading. A closer look was given to problems with different crack configurations and how non-circularity of cracks affects the overall fatigue life of the cylinder when combined with other factors in comparison with circular crack only configurations.

Low Cycle Fatigue Behavior of Welded Components: A New Approach — Experiments and Numerical Simulation

2012 ◽  
Author(s):  
Eliane Lang ◽  
Jürgen Rudolph ◽  
Thomas Beier ◽  
Michael Vormwald
Keyword(s):  
Fatigue Life ◽  
Thermal Loading ◽  
Weld Seam ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Curve ◽  
Life Assessment ◽  
New Approach ◽  
Elastic Plastic ◽  
Weld Seams

Nuclear power plant components are often subjected to local plastic deformations due to low cycle operational thermal loading conditions. The fatigue behavior of weld seams is of particular interest in this context. Applicable design codes for fatigue life assessment use factors (e.g. Fatigue strength reduction factors – FSRF) within the simplified elastic-plastic or general elastic-plastic analysis in connection with the design fatigue curves for non-welded components. This way, the influence of the weld seam on the fatigue behavior is approximately considered. Emanating from this status quo ideas for a new approach considering the particularities of the fatigue behavior of the weld seam in more detail are developed. The proposed approach is based on material mechanics and constitutes a combination of experimental findings and numerical calculations in order to determine the local strains and the fatigue relevant influence of geometrical and metallurgical notches induced by the weld seam. Experiments on welded specimens provide the fatigue life as well as the stabilized cyclic stress-strain curve as relevant input parameters for the finite element analyses. The proposed model is capable of considering the exact geometry of the weld seam obtained by 3D scanning with very high resolution and the different material strengths due to the weld. The consideration of the principal influences on the fatigue behavior of weld seams paves the way to the application of established damage parameters such as PJ with the future objective to transfer the results also on arbitrary proportional and non-proportional loadings with variable amplitudes.

Surface integrity generated with peripheral milling and the effect on low-cycle fatigue performance of aeronautic titanium alloy Ti-6Al-4V

2017 ◽  
Vol 122 (1248) ◽  
pp. 316-332 ◽  
Author(s):  
D. Yang ◽  
Z. Liu
Keyword(s):  
Residual Stress ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Surface Integrity ◽  
Stress Concentration Factor ◽  
Concentration Factor ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Micro Hardness

ABSTRACTMachining-induced surface integrity has an important effect on reliability and service life of the components used in the aerospace industry where titanium alloy Ti-6Al-4V is widely applied. Characterisation of machining-induced surface integrity and revealing its effect on fatigue life are conducive to structural fatigue life optimisation design. In the present study, surface topography, residual stress, microstructure and micro-hardness were first characterised in peripheral milling of titanium alloy Ti-6Al-4V. Then, low-cycle fatigue performances of machined specimens were investigated on the basis of the tension-tension tests. Finally, the effects of surface integrity factors (stress concentration factor, residual stress and micro-hardness) on fatigue performances were discussed. Results show that stress concentration can reduce the fatigue life while increasing the residual compressive stress, and micro-hardness is beneficial to prolonging the fatigue life, but when the surface material of the specimen is subjected to plastic deformation due to yield, the residual stress on the surface is relaxed, and the effect on the fatigue performance is disappeared. Under the condition of residual stress relaxation, the stress concentration factor is the main factor to determine the low-cycle fatigue life of titanium alloy Ti-6Al-4V. While for the specimens with no residual stress relaxation, micro-hardness was the key factor to affect the fatigue life, followed by residual stress and stress concentration factor, respectively.

scholarly journals Effects of Machined Surface Integrity on High-Temperature Low-Cycle Fatigue Life and Process Parameters Optimization of Turning Superalloy Inconel 718

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2428
Author(s):  
Xiaoping Ren ◽  
Zhanqiang Liu ◽  
Xiaoliang Liang ◽  
Pengcheng Cui
Keyword(s):  
Residual Stress ◽  
High Temperature ◽  
Fatigue Life ◽  
Process Parameters ◽  
Surface Integrity ◽  
Inconel 718 ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Machined Surface ◽  
Machined Surface Integrity

Machined surface integrity characteristics, including surface stresses, physical-mechanical properties and metallographic structures, play important roles in the fatigue performance of machined components. This work aimed at investigating the effects of machined surface integrity on high-temperature low-cycle fatigue life. The process parameters were optimized to obtain required surface integrity and fatigue life of the turning superalloy Inconel 718. The relationships between low-cycle fatigue life and machined surface integrity characterization parameters were established based on the low-cycle fatigue tests at a high temperature (650 °C). The sensitivities of turning process parameters to high-temperature low-cycle fatigue life were analyzed, and the optimization parameters were proposed with the goal of antifatigue manufacturing. Experimental results indicated that the impact order of the characterization parameters of machined surface integrity on the high-temperature low-cycle fatigue life were the degree of work hardening RHV, the residual stress in the cutting speed direction S22, the fatigue stress concentration factor Kf, the degree of grain refinement RD and the residual stress in the feed direction S33. In the range of turning parameters of the experiments in this research, the cutting speeds could be 80~110 m/min, and the feed rate could be 0.10~0.12 mm/rev to achieve a longer high-temperature low-cycle fatigue life. The results can be used for guiding the fatigue-resistant manufacturing research of aeroengine superalloy turbine disks.

Fatigue Life Prediction of an Autofrettaged Thick-Walled Pressure Vessel With an External Groove

1991 ◽  
Vol 113 (3) ◽  
pp. 368-374 ◽  
Author(s):  
S. K. Koh ◽  
R. I. Stephens
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Concentration ◽  
Pressure Vessel ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Fatigue Life Prediction ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Operating Stress

An autofrettaged thick-walled pressure vessel with an external groove subjected to a pulsating internal pressure can have fatigue failures at the external groove root due to the combination of tensile autofrettage residual stress, operating stress, and stress concentration. To predict the fatigue life of the autofrettaged thick-walled pressure vessel with an external groove, the local strain approach was applied. The residual stress distribution due to autofrettage and the operating stress distribution due to internal pressure were determined using finite element analysis which resulted in theoretical stress concentration factors. To account for the mean stress effects on the fatigue life prediction of the pressure vessel, low-cycle fatigue behavior with several strain ratios was obtained using smooth axial specimens taken from the ASTM A723 thick-walled steel pressure vessel. Fatigue life predictions were made by incorporating the local strains determined from the linear rule and Neuber’s rule and the Morrow and SWT mean stress parameters determined from low-cycle fatigue tests. The predicted fatigue lives were within factors of 2 to 4, compared to simulated experimental fatigue lives based upon fatigue cracks of 2.5 mm in length. These procedures appear to be realistic for evaluating fatigue lives for this complex pressure vessel.

The Effects of UIT in the Fatigue Life of Al 2024-T3

2010 ◽  
Vol 449 ◽  
pp. 15-22 ◽  
Author(s):  
Martin Castillo-Morales ◽  
A. Salas-Zamarripa
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Low Temperatures ◽  
Compressive Residual Stress ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Impact Frequency ◽  
Ultrasonic Impact Treatment ◽  
Al 2024

The Ultrasonic Impact Treatment (UIT) has been used in different materials to reduce residual welding tensile stresses and improve the fatigue life of welded joints, and also to increase the fatigue resistance at low temperatures. The main aim of this research was to explore the effects of UIT in the fatigue life of a 2024-T3 aluminium alloy. Load controlled fatigue tests were carried out at high and low cycle fatigue, and three UIT parameters at a carrier frequency of 36 kHz were evaluated. These parameters were feed rate, amplitude under load and impact frequency. The results revealed an increase in compressive residual stress and microhardness, as well as some evidence of porosity. However, the fatigue life was reduced drastically. The possible causes of this decrease are still under discussion.

scholarly journals Low cycle fatigue life prediction in shot-peened components of different geometries-part I: residual stress relaxation

2016 ◽  
Vol 40 (5) ◽  
pp. 761-775 ◽  
Author(s):  
C. You ◽  
M. Achintha ◽  
K. A. Soady ◽  
N. Smyth ◽  
M. E. Fitzpatrick ◽  
...  
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Relaxation ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Fatigue Life Prediction ◽  
Cycle Fatigue ◽  
Residual Stress Relaxation

scholarly journals Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications

2003 ◽  
Author(s):  
Paul S. Preve´y ◽  
Ravi A. Ravindranath ◽  
Michael Shepard ◽  
Timothy Gabb
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Case Studies ◽  
Shot Peening ◽  
Damage Tolerance ◽  
Cold Work ◽  
Fatigue Performance ◽  
Surface Enhancement ◽  
Low Plasticity Burnishing ◽  
Life Improvement

Surface enhancement technologies such as shot peening, laser shock peening (LSP), and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The x-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including: • The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing the fatigue benefit of thermal stability at engine temperatures. • An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. • Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. • Corrosion fatigue mitigation with LPB in Carpenter 450 steel. • Damage tolerance improvement in 17-4PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine operating temperatures.

scholarly journals Case Studies of Fatigue Life Improvement Using Low Plasticity Burnishing in Gas Turbine Engine Applications

2006 ◽  
Vol 128 (4) ◽  
pp. 865-872 ◽  
Author(s):  
Paul S. Preve´y ◽  
Ravi A. Ravindranath ◽  
Michael Shepard ◽  
Timothy Gabb
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Case Studies ◽  
Shot Peening ◽  
Damage Tolerance ◽  
Cold Work ◽  
Fatigue Performance ◽  
Surface Enhancement ◽  
Low Plasticity Burnishing ◽  
Life Improvement

Surface enhancement technologies such as shot peening, laser shock peening, and low plasticity burnishing (LPB) can provide substantial fatigue life improvement. However, to be effective, the compressive residual stresses that increase fatigue strength must be retained in service. For successful integration into turbine design, the process must be affordable and compatible with the manufacturing environment. LPB provides thermally stable compression of comparable magnitude and even greater depth than other methods, and can be performed in conventional machine shop environments on CNC machine tools. LPB provides a means to extend the fatigue lives of both new and legacy aircraft engines and ground-based turbines. Improving fatigue performance by introducing deep stable layers of compressive residual stress avoids the generally cost prohibitive alternative of modifying either material or design. The x-ray diffraction based background studies of thermal and mechanical stability of surface enhancement techniques are briefly reviewed, demonstrating the importance of minimizing cold work. The LPB process, tooling, and control systems are described. An overview of current research programs conducted for engine OEMs and the military to apply LPB to a variety of engine and aging aircraft components are presented. Fatigue performance and residual stress data developed to date for several case studies are presented including the following. (1) The effect of LPB on the fatigue performance of the nickel based super alloy IN718, showing the fatigue benefit of thermal stability at engine temperatures. (2) An order of magnitude improvement in damage tolerance of LPB processed Ti-6-4 fan blade leading edges. (3) Elimination of the fretting fatigue debit for Ti-6-4 with prior LPB. (4) Corrosion fatigue mitigation with LPB in Carpenter 450 steel. (5) Damage tolerance improvement in 17-4 PH steel. Where appropriate, the performance of LPB is compared to conventional shot peening after exposure to engine operating temperatures.

A Comprehensive Model for Predicting Fatigue Life of Laser Welded Lap Joint of Galvanized High Strength Steel as a Function of Residual Stresses

2012 ◽  
Author(s):  
Joe Anago ◽  
Fanrong Kong ◽  
Blair Carlson ◽  
Radovan Kovacevic
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Thermal Loading ◽  
Axial Stress ◽  
Three Dimensional ◽  
Element Model ◽  
Lap Joints ◽  
Lap Joint

This paper presents a three-dimensional (3D) multi-physics finite element model (FEM) to predict the fatigue life of a laser welded lap joint of dual phase (DP) 980 steel sheets based upon the level of residual stress. A FEM-based thermal analysis is first performed to numerically predict the welding-induced temperature field combined with the corresponding experimental verification. The temperature histories are then loaded into the mechanical model as thermal loading to numerically calculate the evolution curves of thermally induced stress in order to calculate the level of residual stresses after cooling to room temperature. In order to calculate the equivalent fatigue strength in the laser-welded lap joint, the resultant multi-axial stress (including the induced residual stress (RS) result) is loaded into the equivalent uni-axial stress equation via the Sine Method (SM) in order to achieve the stress curve as a function of the loading cycles. A series of fatigue tests of lap joints are also performed in order to achieve the S-N curves, from which an empirical function between the alternating stress and loading cycle is derived in order to predict the fatigue life of the DP980 lap joint. Finally, the maximum fatigue strength can be predicted numerically through the proposed FEM instead of using experimental trials. The numerical results show that a greater temperature gradient and residual stress are mainly located within the fusion zone (FZ) and close to the heat affected zone (HAZ). The residual stress plays an important role in deciding the final fatigue strength and failure of the DP980 lap joint. An X-ray diffraction technique is used to experimentally measure the residual stress distribution within the weld, for which the numerically predicted results exhibit a good agreement. Also, the numerical simulation and experimental measurements of the fatigue life versus the applied load show a good correlation of results.

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