scholarly journals Fatigue Failure from Inner Surfaces of Additive Manufactured Ti-6Al-4V Components

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 737
Author(s):  
Joel de Jesus ◽  
José António Martins Ferreira ◽  
Luís Borrego ◽  
José D. Costa ◽  
Carlos Capela
Keyword(s):  
Crack Initiation ◽  
Life Prediction ◽  
External Surface ◽  
Fatigue Behavior ◽  
Internal Surface ◽  
Fatigue Loading ◽  
Complex Geometries ◽  
Good Tool ◽  
Lack Of Fusion ◽  
Fusion Defect

Selective laser melting (SLM) is an additive manufacturing process for producing metallic components with complex geometries. A drawback of this process is the process-inherent poor surface finish, which is highly detrimental in materials submitted to fatigue loading situations. The goal of this work is to analyze the fatigue behavior of Ti-6Al-4V specimens with internal axial channels under the following different conditions: hole drilled, hole as manufactured, and hole threaded M4 × 0.7. All the cases studied showed a lower fatigue performance as compared with solid samples due to the surface roughness and geometry effect that produced a surface stress concentration leading to a reduction in fatigue strength. The fractography revealed that crack initiation occurred from the internal surface in all specimens with internal channel mostly from defects as unfused particles and lack of fusion zones, while for the solid specimens crack initiation was observed from the external surface due to insufficient fusion defect. The application of the Smith-Watson-Topper energy-based parameter was revealed to be a good tool for fatigue life prediction of the different series studied.

scholarly journals Low-Cycle Fatigue Crack Initiation Simulation and Life Prediction of Powder Superalloy Considering Inclusion-Matrix Interface Debonding

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 4018
Author(s):  
Shuming Zhang ◽  
Yuanming Xu ◽  
Hao Fu ◽  
Yaowei Wen ◽  
Yibing Wang ◽  
...  
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Low Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Interface Debonding ◽  
Damage Evolution Equation ◽  
Finite Element Software

From the perspective of damage mechanics, the damage parameters were introduced as the characterizing quantity of the decrease in the mechanical properties of powder superalloy material FGH96 under fatigue loading. By deriving a damage evolution equation, a fatigue life prediction model of powder superalloy containing inclusions was constructed based on damage mechanics. The specimens containing elliptical subsurface inclusions and semielliptical surface inclusions were considered. The CONTA172 and TARGE169 elements of finite element software (ANSYS) were used to simulate the interfacial debonding between the inclusions and matrix, and the interface crack initiation life was calculated. Through finite element modeling, the stress field evolution during the interface debonding was traced by simulation. Finally, the effect of the position and shape size of inclusions on interface debonding was explored.

Fatigue Life Prediction for Short Dents in Petroleum Pipelines

2002 ◽  
Author(s):  
Adam J. Rinehart ◽  
Peter B. Keating
Keyword(s):  
Fatigue Life ◽  
Crack Initiation ◽  
Crack Propagation ◽  
External Force ◽  
Life Prediction ◽  
Fatigue Behavior ◽  
Contact Region ◽  
Fatigue Cracking ◽  
Fatigue Life Prediction ◽  
Crack Initiation Life

Pipeline dent fatigue behavior has been shown to be strongly dependent upon dent length and external force dent restraint characteristics. Full-scale laboratory tests have shown that short dents that are unrestrained by an external force typically experience fatigue cracking in the dent periphery outside of the dent contact region. A fatigue life prediction method for short dents is presented here. In order to assess method accuracy, predictions are made for cases in which fatigue life has been measured experimentally. The predictions account for both crack initiation life and crack propagation life. Stress concentration values used in the predictions are determined using finite element modelling on a case-by-case basis for comparison purposes. Appropriate crack initiation life estimates, stress intensity factor predictions, and crack propagation models are taken from existing literature. Predicted and measured fatigue lives are compared for the cases studied.

Fractographical Investigation on High-Cycle Fatigue Behavior of Direct Aging GH4169 Superalloy

2014 ◽  
Vol 789 ◽  
pp. 627-632 ◽  
Author(s):  
Li Zhang ◽  
Xue Ren Wu ◽  
Xin Yue Huang ◽  
Xu Dong Li
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Primary Source ◽  
Fatigue Loading ◽  
Cycle Fatigue ◽  
Direct Aging ◽  
Stress Ratios

The present work is aimed at the fatigue crack initiation behavior of the direct aging superalloy GH4169 at 650 °C. Un-notched specimens were tested under high-cycle fatigue loading with the two stress ratios of R = 0.1 and 0.5. Fracture surfaces were examined using field emission scanning electron microscopy (FESEM). Special attention is paid to the crack initiation sites. Two microstructure features in the fatigue crack initiation regions have been observed. One is obviously the feature of the Ti (C,N)-inclusions, and the other is some kinds of facets. The analysis on the facets was carried out by using energy dispersive spectra (EDS). It was found that the elements at the facets are similar to the matrix. However, some inclusions, Nb (C,N), have been found in the subsurface facets in a few specimens. Sometimes, fatigue lives of the specimens for the crack initiating from the inclusions are longer than those of cracks from the facets, depending on the size of inclusions and the depth from sample surface. Crack initiation for most of the specimens occurs at inclusions, and therefore inclusion is a primary source of crack initiation for this alloy.

Prediction of the Rolling Contact Fatigue Behavior of Pre-Indented Hybrid Bearings

2014 ◽  
Author(s):  
Corentin Robitaille ◽  
Daniel Nelias ◽  
Emmanuel Tonicello ◽  
Thibaut Chaise
Keyword(s):  
Crack Initiation ◽  
Fatigue Behavior ◽  
Rolling Contact Fatigue ◽  
Contact Fatigue ◽  
Fatigue Loading ◽  
Rolling Contact ◽  
Computational Time ◽  
Plastic Behavior ◽  
Rolling Element ◽  
Crack Initiation Criterion

The objective of this work is to study the Rolling Contact Fatigue (RCF) behavior of hybrid bearings. The studied bearings are composed of Si3N4 balls rolling on steel raceways. The raceways are made out of nitrided 32CrMoV13 steel. The nitriding treatment aims at reinforcing the surface mechanical properties. As the presence of an indent on the raceway surface will dramatically decrease the fatigue life of the rolling element [1], this study focuses on the RCF behavior of pre-indented rolling element bearings. It is thus necessary to study the fatigue behavior of both the steel and the ceramic material under fatigue loading. The study presented here focuses on the fatigue behavior of nitrided 32CrMoV13 steel under rolling contact and aims at proposing a crack initiation criterion based on experimental results. Fatigue tests are performed on a bi-disks machine with indented 32CrMoV13 samples to observe the damage evolution and crack initiation stages under various indent dimensions and test conditions. In parallel simulations are performed with a semi-analytical method to accurately determine the stress history under elastic-plastic rolling contact. Semi analytical methods, classically used for the simulation of elastic contacts, have recently been extended to the consideration of plasticity [2], allowing to simulate the ball-raceway interaction in ball bearings [3] and wear or running in [4]. The main advantage of these methods is their ability to simulate the coupling between the contact conditions and the plastic behavior in reasonable computational time. Based on the experimental and simulation results, a crack initiation criterion based on the dislocation theory proposed by Tanaka and Mura [5] is proposed allowing to predict the number of cycles for crack initiation for the given material.

Kerusakan Pada Material Pipa Air Bersih Akibat General Corrosion

2019 ◽  
Vol 16 (2) ◽  
Author(s):  
M. N. Setia Nusa
Keyword(s):  
Chemical Composition ◽  
Failure Analysis ◽  
External Surface ◽  
Internal Surface ◽  
General Corrosion ◽  
Water Pipe ◽  
Corrosion Attack ◽  
Corrosion Failure ◽  
Environment Factor

Water pipe of 4.5” diameter and has been operated for 8 year having failure due to corrosion attack on its external and internal surface. It is conducted failure analysis to find out the cause of corrosion by having testing examination of visual fractography, metalography,, SEM EDAX, hardness and chemical composition. Testing and examination results show that the failure / corroded pipe has a for in of general corrosion on the external surface due to environment factor or ground factor arround the pipe and on the internal surface was influenced by excessive root weld creating protrude which then causing turbolens and deposite to accelerate corrosion attack.Pipa berdiameter 4.5” yang berfungsi mengalirkan air bersih dan telah beroperasi selama 8 tahun, terjadi kerusakan berbentuk korosi pada permukaan luar pipa dan permukaan dalam. Untuk itu dilakukan analisa kerusakan untuk mengetahui penyebab terjadinya korosi dengan pengujian dan pemeriksaan secara visual,Fractography, Metallography, SEM, EDAX, Uji Kekerasan dan Uji Komposisi Kimia. Hasil pemeriksaan dan pengujian pada pipa yang rusak / korosi berbentuk jenis general korosi pada permukaan luar pipa yang diakibatkan faktor lingkungan atau tanah disekitar pipa, sedangkan pada bagian dalam pipa dipengaruhi oleh adanya lelehan pengelasan yang kurang sempurna sehingga menimbulkan benjolan yang mengakibatkan aliran air didalam pipa tidak lancar sehingga terjadi turbolensi yang menimbulkan endapan dan mengakibatkan percepatan terjadinya korosi.Keywords: Pipe, environtment, turbolens, corrosion, failure

scholarly journals Experimental Determination of the Heat Transfer Coefficient of Real Cooled Geometry Using Linear Regression Method

Energies ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 180
Author(s):  
Asif Ali ◽  
Lorenzo Cocchi ◽  
Alessio Picchi ◽  
Bruno Facchini
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Linear Regression ◽  
Surface Temperature ◽  
Transfer Coefficient ◽  
External Surface ◽  
Internal Surface ◽  
Regression Method ◽  
Thermal Transient

The scope of this work was to develop a technique based on the regression method and apply it on a real cooled geometry for measuring its internal heat transfer distribution. The proposed methodology is based upon an already available literature approach. For implementation of the methodology, the geometry is initially heated to a known steady temperature, followed by thermal transient, induced by injection of ambient air to its internal cooling system. During the thermal transient, external surface temperature of the geometry is recorded with the help of infrared camera. Then, a numerical procedure based upon a series of transient finite element analyses of the geometry is applied by using the obtained experimental data. The total test duration is divided into time steps, during which the heat flux on the internal surface is iteratively updated to target the measured external surface temperature. The final procured heat flux and internal surface temperature data of each time step is used to find the convective heat transfer coefficient via linear regression. This methodology is successfully implemented on three geometries: a circular duct, a blade with U-bend internal channel, and a cooled high pressure vane of real engine, with the help of a test rig developed at the University of Florence, Italy. The results are compared with the ones retrieved with similar approach available in the open literature, and the pros and cons of both methodologies are discussed in detail for each geometry.

scholarly journals Evaluation of Transverse Crack Initiation in Cross-Ply CFRP Laminates under Fatigue Loading

2011 ◽  
Vol 77 (779) ◽  
pp. 1123-1134 ◽  
Author(s):  
Keigo TAKAMURA ◽  
Atsushi HOSOI ◽  
Narumichi SATO ◽  
Hiroyuki KAWADA
Keyword(s):  
Crack Initiation ◽  
Transverse Crack ◽  
Fatigue Loading ◽  
Cfrp Laminates

Very High Cycle Fatigue Behavior and Life Prediction of a Low Strength Weld Metal at Moderate Temperature

2011 ◽  
Author(s):  
Ming-Liang Zhu ◽  
Fu-Zhen Xuan ◽  
Zhengdong Wang
Keyword(s):  
Crack Initiation ◽  
Weld Metal ◽  
Room Temperature ◽  
Fatigue Behavior ◽  
Fatigue Properties ◽  
Dissimilar Welding ◽  
Initiation Mechanism ◽  
Metallic Inclusions ◽  
Low Strength ◽  
Very High

The fatigue properties of a low strength weld metal in a dissimilar welding joint in high cycle and very high cycle regimes were investigated by fully reversed axial tests in air at room temperature and 370°C. A clear duplex S-N curve existed as a result of the transition of fatigue failure mode from surface-induced failure to internal-induced failure at 370°C, while the S-N curve was continuously decreased at room temperature. A new model was successfully proposed to predict fatigue life, and interpret the crack initiation modes transition from surface inclusion to interior inclusion. It was concluded that cracks were initiated by competition among non-metallic inclusions, welding pores and discontinuous microstructures in high cycle regime. While in the very high cycle regime, non-metallic inclusions were the dominant crack initiation mechanism which depended on stress level, inclusion size as well as inclusion depth.

Sign in / Sign up

Export Citation Format

Share Document