Porosity in Aluminum Alloy Castings

2019 ◽  
Author(s):  
Lenka Kuchariková ◽  
Eva Tillová ◽  
Juraj Belan ◽  
Milan Uhríčik
Keyword(s):  
Fatigue Life ◽  
Material Properties ◽  
Cast Alloy ◽  
Fatigue Behavior ◽  
Casting Process ◽  
Sand Mold ◽  
Fatigue Properties ◽  
Behavior Changes ◽  
Metallic Mold ◽  
Alloy Castings

The inclusions and impurities (such as oxides, carbide, defect, and so on) are formed mostly during the casting process. These inclusions and impurities reduce material properties because an increase in porosity has a tendency to form failure and corrosion of aluminum alloys. The effect of porosity on the fatigue life of AlSi9Cu3 cast alloy was studied, examining the effect of porosity size, distribution, and morphology on the fatigue behavior changes, using image analysis software. A comparison of the fatigue properties was made between material casted into a metallic mold and the material casted into a sand mold under the same conditions of gravity die casting. The fatigue properties were studied on equipment Vibrophores Amsler 50–250 HFP 5100 for material casted into a metallic mold and on Rotoflex for materials casted into a sand molds. The results show that porosity has the greatest detrimental effect on fatigue life. It was found that fatigue life decreases with increasing size of the pores surface. The experimental material casted into the metallic mold had about 98.78% smaller porosity size in comparison to the material casted into the sand mold; therefore, it showed better fatigue and mechanical properties.

scholarly journals Quantitative Analysis of Inclusion Engineering on the Fatigue Property Improvement of Bearing Steel

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 476 ◽  
Author(s):  
Chao Gu ◽  
Min Wang ◽  
Yanping Bao ◽  
Fuming Wang ◽  
Junhe Lian
Keyword(s):  
Fatigue Life ◽  
Quantitative Analysis ◽  
Critical Size ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Property ◽  
Bearing Steel ◽  
Fatigue Properties ◽  
Bearing Steels ◽  
Inclusion Distribution

The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design.

Influence of Wear Properties on Fretting Fatigue Life of a CK45 Alloy and the Al7175 Alloy

2008 ◽  
Vol 587-588 ◽  
pp. 971-975 ◽  
Author(s):  
M. Buciumeanu ◽  
A.S. Miranda ◽  
F.S. Silva
Keyword(s):  
Wear Resistance ◽  
Fatigue Life ◽  
Material Properties ◽  
Fatigue Behavior ◽  
Synergetic Effect ◽  
Fretting Fatigue ◽  
Reduction Factor ◽  
Strength Reduction ◽  
Strength Reduction Factor ◽  
Wear Properties

The main objective of this work was to study the influence of the wear properties of two commercial alloys (CK45 and Al7175) on their fretting fatigue behavior. It is verified the effect of material local degradation by wear on a fatigue strength reduction factor, namely the stress concentration factor, and on the overall fretting fatigue life of these materials. The fretting fatigue phenomenon is a synergetic effect between wear and fatigue. It is dependent on both the fatigue and the wear properties of the materials. Material properties promoting an increase in wear resistance should enhance fretting fatigue life.

Damage and fatigue analysis of AA7050-T7451 plate with cold expanded hole based on a micro-void evolution model

2019 ◽  
Vol 54 (2) ◽  
pp. 105-115
Author(s):  
Fengmei Xue ◽  
Fuguo Li ◽  
Xiaolei Cui
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Complex Stress ◽  
Evolution Model ◽  
Fatigue Properties ◽  
Strengthening Effect ◽  
Void Evolution ◽  
Cold Worked ◽  
Three Dimensional Finite Element

The ultimate tensile strength and fatigue life of plate with cold worked hole under high loading are always key designing parameters in engineering field. In this article, different cold expanded degrees (ranging from 1.69% to 11.11%) are applied to plate specimens with a central hole, made of 7050-T7451 aluminum alloy. The damage and fatigue properties are investigated by the three-dimensional finite element method with a user subroutine embedded into a void evolution model under complex stress states. The damage analysis indicates that plastic damage becomes critical when the cold expanded degree is larger than 7.14%, which does not suit for further service due to the loss of toughness. The cold expanded degree of 5.26% is identified as the best. It can be found that the fatigue life improves with the increased cold expanded degree. The small cold expanded degree leads to poor strengthening effect because of lacking sufficient residual stress, while large cold expanded degree makes micro-cracks emerge, which is beneficial to the increase in strengthening. All these results prove that the numerical analysis can accurately predict fatigue behavior of AA7050-T7451 plate based on our proposed approach, which is expected to be a powerful method in engineering field.

scholarly journals Effect of UV Ageing on the fatigue life of bulk polyethylene

2018 ◽  
Vol 165 ◽  
pp. 08002 ◽  
Author(s):  
Hamza Lamnii ◽  
Moussa Nait-Abdelaziz ◽  
Georges Ayoub ◽  
Jean-Michel Gloaguen ◽  
Ulrich Maschke ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Uv Irradiation ◽  
Chemical Structure ◽  
Fatigue Behavior ◽  
Crystalline Polymer ◽  
Fatigue Loading ◽  
Chain Scission ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Irradiation Effect

Polymers operating in various weathering conditions must be assessed for lifetime performance. Particularly, ultraviolet (UV) radiations alters the chemical structure and therefore affect the mechanical and fatigue properties. The UV irradiation alters the polymer chemical structure, which results into a degradation of the mechanical and fatigue behavior of the polymer. The polymer properties degradation due to UV irradiation is the result of a competitive process of chain scission versus post-crosslinking. Although few studied investigated the effect of UV irradiation on the mechanical behaviour of thermoplastics, fewer examined the UV irradiation effect on the fatigue life of polymers. This study focuses on investigating the effect of UV irradiation on the fatigue properties of bulk semi-crystalline polymer; the low density Polyethylene (LDPE). Tensile specimens were exposed to different dose values of UV irradiation then subjected to fatigue loading. The fatigue tests were achieved under constant stress amplitude at a frequency of 1Hz. The results show an important decrease of the fatigue limit with increasing absorbed UV irradiation dose.

Effect of Bias Voltage on Fatigue Behavior of CrN Film Deposited on Ti-6Al-4V Alloy

2008 ◽  
Author(s):  
Md. Shamimur Rahman ◽  
Daisuke Yonekura ◽  
Takeshi Katsuma ◽  
Ri-Ichi Murakami
Keyword(s):  
Fatigue Life ◽  
Bias Voltage ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Substrate Surface ◽  
Film Deposition ◽  
Fatigue Properties ◽  
Ion Plating ◽  
Coated Substrate ◽  
Coating Composite

PVD technique incorporating CrN coating was applied to the titanium alloy (Ti-6Al-4V) and its effects on the fatigue life and fatigue strength were studied in this paper to explore the fatigue behavior of Ti-6Al-4V specimens. A CrN film deposited by arc ion plating (AIP) improved the mechanical properties; specially hardness and fatigue life of Ti-6Al-4V specimens. The properties were studied using XRD, hardness and fatigue testers. The fatigue life of CrN-coated Ti-6Al-4V specimens was improved significantly compared to those of uncoated specimens. The enhanced fatigue life can be attributed to the improved hardness of CrN film due to change of bias voltage during the film deposition. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the substrate surface. It has been determined that the fatigue fracture of the substrate-coating composite is dominated by the fracture of the CrN film since fatigue cracks have been observed to form first at the surface of the film and subsequently to propagate towards the substrate. It has also been concluded that the increase in fatigue properties of the coated substrate is associated mainly with the changing of bias voltage during the coating observed in most of the maximum alternating stress range explored in this work.

Fatigue Behavior of Ferritic-Pearlitic-Bainitic Steel – Effect of Positive Mean Stress

2009 ◽  
Vol 417-418 ◽  
pp. 577-580
Author(s):  
Jaroslav Polák ◽  
Martin Petrenec
Keyword(s):  
Fatigue Life ◽  
Plastic Strain ◽  
Strain Amplitude ◽  
Fatigue Behavior ◽  
Cyclic Creep ◽  
Plastic Strain Amplitude ◽  
Fatigue Properties ◽  
Mean Stress ◽  
Bainitic Steel ◽  
The Mean

The fatigue properties of ferritic-pearlitic-bainitic steel using specimens produced from massive forging were measured in stress controlled regime with positive mean stress. The cyclic creep curves and cyclic hardening/softening curves were evaluated. The fatigue life was plotted in dependence on the mean stress and on the plastic strain amplitude. The principal contribution to the drop of the fatigue life with the mean stress is due to the increase of the plastic strain amplitude in cycling with mean stress.

scholarly journals The Fatigue Behavior and Mechanism of Large FV520B-I Specimens in a Very High Cycle Regime

2021 ◽  
Author(s):  
Han Zhang ◽  
Ming Zhang ◽  
Li Meng Li ◽  
Bao Hai Xie ◽  
Jun Li Zhang
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Inclusion Size ◽  
Fatigue Properties ◽  
Corrosion Fatigue Crack ◽  
Life Model ◽  
Specimen Test ◽  
Ultrasonic Fatigue ◽  
Very High

Abstract We examined the fatigue properties in very high cycle regime of large FV520B-I specimens in an ultrasonic fatigue test. The fatigue mechanism in very high cycle regime didn’t change and the fatigue properties obviously degraded as the specimen size enlarged. The fatigue life decreased and the S-N curve moved downward due to the increase of inclusion size in large specimens. The maximum inclusion sizes in specimens were predicted by the method of statistics of extreme value. The prediction of fatigue strength using the modified Murakami model was closer to the test result, and the fitting of fatigue life using the corrosion fatigue crack initiation life model was less effective compared with the fitting of small specimen test results

scholarly journals Ratcheting-Fatigue Behavior of Harmonic-Structure-Designed SUS316L Stainless Steel

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 477
Author(s):  
Yang Song ◽  
Zhe Zhang ◽  
Hantuo Ma ◽  
Masashi Nakatani ◽  
Mie Ota Kawabata ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Stainless Steels ◽  
Fatigue Behavior ◽  
Structure Design ◽  
Control Mode ◽  
Fatigue Properties ◽  
Mean Stress ◽  
Strain Accumulation ◽  
Harmonic Structure ◽  
Ratcheting Strain

Stainless steels with harmonic-structure design have a great balance of high strength and high ductility. Therefore, it is imperative to investigate their fatigue properties for engineering applications. In the present work, the harmonic-structured SUS316L stainless steels were fabricated by mechanical milling (MM) and subsequent hot isostatic pressing (HIP) process. A series of ratcheting-fatigue tests were performed on the harmonic-structured SUS316L steels under stress-control mode at room temperature. Effects of grain structure and stress-loading conditions on ratcheting behavior and fatigue life were investigated. Results showed that grain size and applied mean stress had a significant influence on ratcheting-strain accumulation and fatigue life. Owing to the ultrafine grained structure, tensile strength of the harmonic-structured SUS316L steels could be enhanced, which restrained the ratcheting-strain accumulation, resulting in a prolonged fatigue life. A higher mean stress caused a faster ratcheting-strain accumulation, which led to the deterioration of fatigue life. Moreover, a modified model based on Smith–Watson–Topper (SWT) criterion predicted the ratcheting-fatigue life of the harmonic-structured SUS316L steels well. Most of the fatigue-life points were located in the 5 times error band.

scholarly journals The Effect of Laser Peening without Coating on the Fatigue of a 6082-T6 Aluminum Alloy with a Curved Notch

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 728 ◽  
Author(s):  
Enrico Troiani ◽  
Nicola Zavatta
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Life ◽  
Residual Stresses ◽  
Fatigue Behavior ◽  
Surface Hardness ◽  
Element Model ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Laser Peening ◽  
Laser Peening Without Coating

Laser shock peening has established itself as an effective surface treatment to enhance the fatigue properties of metallic materials. Although a number of works have dealt with the formation of residual stresses, and their consequent effects on the fatigue behavior, the influence of material geometry on the peening process has not been widely addressed. In this paper, Laser Peening without Coating (LPwC) is applied at the surface of a notch in specimens made of a 6082-T6 aluminum alloy. The treated specimens are tested by three-point bending fatigue tests, and their fatigue life is compared to that of untreated samples with an identical geometry. The fatigue life of the treated specimens is found to be 1.7 to 3.3 times longer. Brinell hardness measurements evidence an increase in the surface hardness of about 50%, following the treatment. The material response to peening is modelled by a finite element model, and the compressive residual stresses are computed accordingly. Stresses as high as −210 MPa are present at the notch. The ratio between the notch curvature and the laser spot radius is proposed as a parameter to evaluate the influence of the notch.

Fatigue Life Prediction of Al-Li Alloy Butt-Welded Joints in Aerospace Structures

2009 ◽  
Author(s):  
Muhammad A. Wahab ◽  
Vinay Raghuram
Keyword(s):  
Fatigue Life ◽  
Crack Propagation ◽  
Life Prediction ◽  
Space Shuttle ◽  
Fatigue Behavior ◽  
Fatigue Life Prediction ◽  
Fatigue Properties ◽  
Interface Element ◽  
Aerospace Structures ◽  
Friction Stir

Friction-Stir-Welding (FSW) has been adopted as a major process for welding Aluminum aerospace structures. AA-2195 is one of the new generations Aluminum alloy (Al-Li) that has been used on the new super lightweight external tank of the space shuttle. The Lockheed Martin Space Systems (LMSS), Michaud Operations in New Orleans is continuously pursuing FSW technologies in its efforts to advance fabrication of the external tanks of the space shuttle. The future launch vehicles which will have to be reusable, mandates the structure to have good fatigue properties, which prompts an investigation into the fatigue behavior of the friction-stir-welded aerospace structures. The butt-joint specimens of Al-2195 are fatigue tested according to ASTM-E647. The effect of Stress ratios, Corrosion-Preventive-Compound (CPC), and periodic Overloading on fatigue life is investigated. Scanning Electron Microscopy (SEM) is used to examine the failure surfaces and examine the different modes of crack propagation i.e. tensile, shear, and brittle modes. It is found that fatigue life increases with the increase in stress ratio, the fatigue life increases from 30–38% with the use of CPC, the fatigue life increases 8–12 times with periodic overloading; crack closure phenomenon dominates the fatigue facture. Numerical Analysis using FEA has also been used to model fatigue life prediction scheme for these structures, the interface element technique with critical bonding strength criterion for formation of the new surfaces has been used to model crack propagation. The fatigue life predictions made using this method are within the acceptable ranges of 10–20% of the experimental fatigue life. This method overcomes the limitation of the traditional node-release scheme and closely follows the physics of crack propagation.

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