Low Cycle Fatigue Tests With the Use of Miniaturized Test Specimens

2017 ◽  
Author(s):  
Jan Dzugan ◽  
Radek Prochazka ◽  
Pavel Konopik
Keyword(s):  
Residual Life ◽  
Low Cycle Fatigue ◽  
Fem Analysis ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Treatment Development ◽  
Structured Materials ◽  
Testing Procedures ◽  
Large Application

Determination of mechanical properties with the use of sub-sized specimens is topic a high interest nowadays. The application of the sub-sized samples is quite wide for all cases where only limited amount of the experimental material is available such as evaluation of additively manufactured products properties, residual life of in-service components, properties determination of developed nano-structured materials, assessment of dilatometric samples used for thermal and thermo-mechanical treatment development, local properties of components, weld joints and so on. Concerning this large application field it would be very useful to prepare standard for small size samples especially for the most demanded material properties: tensile properties, notch impact transition temperature, fatigue properties, fracture toughness and creep. Current paper is going to deal with the low fatigue (LCF) properties assessment with the use of miniaturized specimens’. There were proposed specimen geometries with the use of FEM analysis and testing procedures for considered mini-specimens tests were developed. In the case of strain controlled LCF tests, contactless testing system had to be established for testing of small sized specimens, where it is not possible to apply standard mechanical extensometers for test control. Moreover, LCF procedure for high temperature tests was also successfully established here. The LCF results were subsequently used for Manson-Coffin parameters determination. Results of low cycle tests for several steels are confronted with the results of standard sized specimens with very good agreement for all considered conditions.

Determination of Local Tensile and Fatigue Properties With the Use of Sub-Sized Specimens

2015 ◽  
Author(s):  
Jan Džugan ◽  
Pavel Konopik ◽  
Martin Rund ◽  
Radek Prochazka
Keyword(s):  
Residual Life ◽  
Tensile Tests ◽  
Test Methods ◽  
Standard Test ◽  
Fatigue Tests ◽  
Supercooled Austenite ◽  
Fatigue Properties ◽  
Standard Size ◽  
Loading Mode

Determination of mechanical properties with the use of sub-sized specimens is very important topic nowadays. The use of sub-sized samples can be quite wide in all cases when limited amount of the experimental material is available such as evaluation of residual life of in-service components, properties determination of developed nano-structured materials, assessment of dilatometric samples used for thermal and thermo-mechanical treatment development, local properties of weld joints and so on. Concerning this large application field it would be very useful to prepare standard for small size samples especially for most demanded material properties: tensile properties, notch impact transition temperature, fatigue properties, fracture toughness and creep. One of the widely used methods of miniature sample testing is Small Punch Test (SPT) that is used for determination of all above mentioned properties. However the main drawback of this method is need of known correlation relation between considered property and SPT for the material of interest. The correlation is needed due to different loading mode in comparison between SPT and standard test methods. Unfortunately, transferability of these correlation parameters between labs is very limited and thus each lab has to determine its own that limits the use of this method. More interest is recently paid to development of small size samples procedures using miniaturized standardized samples maintaining big advantage — the same loading mode between small sized and full sized samples. The same loading mode significantly reduces or completely removes complexity of the results transfer from small to standard size samples. The current paper is dealing with overview of various applications of small sized tensile tests and fatigue tests. Concerning tensile tests quasi static tensile test at room temperature as well as at elevated temperature are show together with results of dynamic tests and special tests of metastable supercooled austenite. The developed procedures performance is demonstrated by comparison of standard size and sub-size specimens results comparison for all tests, except supercooled austenite tests, where no standard size specimen exists.

scholarly journals Fatigue Properties of AZ31B Magnesium Alloy Processed by Equal-Channel Angular Pressing

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1191
Author(s):  
Ryuichi Yamada ◽  
Shoichiro Yoshihara ◽  
Yasumi Ito
Keyword(s):  
Magnesium Alloy ◽  
Equal Channel Angular Pressing ◽  
Low Cycle Fatigue ◽  
Annealed Sample ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Angular Pressing ◽  
Fundamental Research ◽  
Number Of Cycles ◽  
Biodegradable Magnesium

A stent is employed to expand a narrowed tubular organ, such as a blood vessel. However, the persistent presence of a stainless steel stent yields several problems of late thrombosis, restenosis and chronic inflammation reactions. Biodegradable magnesium stents have been introduced to solve these problems. However, magnesium-based alloys suffer from poor ductility and lower than desired fatigue performance. There is still a huge demand for further research on new alloys and stent designs. Then, as fundamental research for this, AZ31 B magnesium alloy has been investigated for the effect of equal-channel angular pressing on the fatigue properties. ECAP was conducted for one pass and eight passes at 300 °C using a die with a channel angle of 90°. An annealed sample and ECAP sample of AZ31 B magnesium alloy were subjected to tensile and fatigue tests. As a result of the tensile test, strength in the ECAP (one pass) sample was higher than in the annealed sample. As a result of the fatigue test, at stress amplitude σa = 100 MPa, the number of cycles to failure was largest in the annealed sample, medium in the ECAP (one pass) sample and lowest in the ECAP (eight passes) sample. It was suggested that the small low cycle fatigue life of the ECAP (eight passes) sample is attributable to severe plastic deformation.

scholarly journals Evaluation of Fatigue Characteristics of Aluminum Alloys and Mechanical Components Using Extreme Value Statistics and C-specimens

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1915
Author(s):  
Jungsub Lee ◽  
Sang-Youn Park ◽  
Byoung-Ho Choi
Keyword(s):  
Aluminum Alloys ◽  
Fem Analysis ◽  
Extreme Value ◽  
Fatigue Tests ◽  
Extreme Value Statistics ◽  
Fatigue Properties ◽  
Chemical Compositions ◽  
Cross Sectional ◽  
Fatigue Characteristics ◽  
Mechanical Components

In this study, the fatigue characteristics of aluminum alloys and mechanical components were investigated. To evaluate the effect of forging, fatigue specimens with the same chemical compositions were prepared from billets and forged mechanical components. To evaluate the cleanliness of the aluminum alloys, the cross-sectional area of specimens was observed, and the maximum inclusion sizes were obtained using extreme value statistics. Rotary bending fatigue tests were performed, and the fracture surfaces of the specimens were analyzed. The results show that the forging process not only elevated the fatigue strength but also reduced the scatter of the fatigue life of aluminum alloys. The fatigue characteristics of C-specimens were obtained to develop finite-element method (FEM) models. With the intrinsic fatigue properties and strain–life approach, the FEM analysis results agreed well with the test results.

Low Cycle Fatigue Properties of FGH720Li Superalloy

2021 ◽  
Vol 1035 ◽  
pp. 292-296
Author(s):  
Zi Chao Peng ◽  
Jun Ying Sheng ◽  
Xu Qing Wang ◽  
Yue Tang
Keyword(s):  
Fatigue Life ◽  
Powder Metallurgy ◽  
Applied Stress ◽  
Low Cycle Fatigue ◽  
Influencing Factor ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Nickel Base Superalloy ◽  
Loading Frequency ◽  
Cycle Fatigue

Low cycle fatigue (LCF) properties of a powder metallurgy(PM) nickel base superalloy FGH720Li were systematically studied in this work, including smooth LCF and notched LCF tested at various temperatures and different stress. The relationship between the fatigue life and applied stress was analyzed both for smooth fatigue and notch fatigue tests. The effects of loading frequency and stress ratio on LCF behavior were also studied. As an important influencing factor of the fatigue life in powder metallurgy superalloy, the effect of inclusions on LCF life was also investigated. The results showed that the fatigue properties of FGH720Li alloy was excellent, when tested at the temperature of 450°C and applied stress of 1230MPa, the fatigue life could exceed 5×104 cycles. When tested at 650°C and 1150MPa, the average fatigue life was still beyond 2×105 cycles.

Model of the Deformation Process under Thermo-Mechanical Fatigue Conditions

2012 ◽  
Vol 726 ◽  
pp. 143-149
Author(s):  
Jerzy Okrajni ◽  
Grzegorz Junak
Keyword(s):  
Deformation Process ◽  
Low Cycle Fatigue ◽  
Hysteresis Loops ◽  
Fatigue Tests ◽  
Mathematical Representation ◽  
Deformation Characteristics ◽  
Cycle Fatigue ◽  
Calculation Algorithm ◽  
Mechanical Fatigue

The paper focuses on the development of a mathematical representation of deformation characteristics under the conditions of an elevated changeable temperature and mechanical loads. The method proposed in the paper is based on the use of characteristics determined in low-cycle fatigue tests at constant temperatures. Hysteresis loops reflecting the behaviour of a material under the conditions of low-cycle loads at an elevated temperature were primarily used. The effect of relaxation on the course of the hysteresis loop was taken into account. The steady state of the material is referred to in the proposed representation. A calculation algorithm was developed to enable the determination of the stress value for subsequent increases of strain over time. The results obtained were compared with experimentally determined characteristics.

Effect of Fiber Volume Fraction on Low Cycle Fatigue Behavior of Al2O3f/Al-Si Composites

2012 ◽  
Vol 268-270 ◽  
pp. 87-91
Author(s):  
Jian Jun Cui ◽  
Bing Chao Li ◽  
Guo Hua Zhang ◽  
Jian Xin Zhang ◽  
Zuo Shan Wei ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Short Fibers ◽  
Fiber Volume ◽  
Large Size

The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

MMC Ring Fatigue and Fracture Life Prediction: An Engineering Model

1993 ◽  
Author(s):  
Gary R. Halford
Keyword(s):  
Crack Initiation ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Tensile Fracture ◽  
Nasa Lewis Research ◽  
Engineering Model ◽  
Current Application ◽  
Strain Compatibility ◽  
The Matrix

Abstract The framework of an engineering creep-fatigue durability model has been adapted for use in estimating the radial static burst pressure and cyclic low-cycle fatigue macro-crack initiation resistance of continuous fiber reinforced (CFR) metal matrix composite (MMC) rings for application at 800 °F. Rings of circumfrentially wrapped SCS6/Ti-15-3 were manufactured by Textron Specialty Metals and burst tested by Pratt & Whitney as a part of a cooperative program with the NASA Lewis Research Center. Fatigue tests have as yet to be performed. The engineering model is based on a 3-D elasto-plastic micromechanics analysis of the tensile-loaded composite architecture. Use is made of the rule of mixtures, strain compatibility, equilibrium, and the stress-strain relationships of the constituents. Knowledge is required of the mechanical and fatigue properties of the matrix and fibers and how the presence of each affects the sharing of imposed stresses and strains. The model addresses specific issues such as residual fabrication stresses, inelastic deformation within the ductile matrix, multiaxial constraint imposed on the matrix, cyclic relaxation of both residual and applied mean stresses in the matrix, fatigue micro-crack initiation and propagation in the matrix, and tensile fracture of both the ductile matrix and the brittle fibers. In the current application of the model, the specific issues were empirically calibrated through use of tensile and tension-tension fatigue coupons that had been subjected to essentially identical loading as the rings.

Low-Cycle-Fatigue Properties of a 17-4 PH Stainless Steel Manufactured via Selective Laser Melting

2021 ◽  
Vol 877 ◽  
pp. 55-60
Author(s):  
Lorenzo Maccioni ◽  
Eleonora Rampazzo ◽  
Filippo Nalli ◽  
Yuri Borgianni ◽  
Franco Concli
Keyword(s):  
Stainless Steel ◽  
Selective Laser Melting ◽  
Low Cycle Fatigue ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Laser Melting ◽  
Softening Behavior ◽  
The One ◽  
Cylindrical Samples

In this paper, the static and low-cycle-fatigue (LCF) behavior of wrought samples of 17-4 PH stainless steel (SS) manufactured via Selective Laser Melting (SLM) are presented. On the one hand, several scholars have studied SLM materials and literature reports a huge amount of data as for the high-cycle-fatigue (HCF) behavior. On the other hand, few are the data available on the LCF behavior of those materials. The aim of the present research is to provide reliable data for an as-build 17-4 PH steel manufactured via SLM techniques. Only with quantitative data, indeed, it is possible to exploit all the advantages that this technology can offer. In this regard, both quasi-static (QS) and low-cycle-fatigue tests were performed on Additive Manufacturing (AM) cylindrical samples. Through QS tests, the constitutive low has been defined. Strain-controlled fatigue tests on an electromechanical machine were performed on 12 samples designed according to the ASTM standard. Tests were continued also after the stabilization was reached (needed for the cyclic curve described with the Ramberg-Osgood equation) to obtain also the fatigue (ε-N) curve. Results show that the material has a softening behavior. The Basquin-Coffin-Manson (BCM) parameters were tuned on the basis of the ε-N combinations after rupture.

Effect of Fiber Volume Fraction on Low Cycle Fatigue Behavior of Al2O3f/Al-Si Composites

2012 ◽  
Vol 622-623 ◽  
pp. 1340-1344
Author(s):  
Jian Jun Cui ◽  
Bing Chao Li ◽  
Guo Hua Zhang ◽  
Jian Xin Zhang ◽  
Zuo Shan Wei ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Short Fibers ◽  
Fiber Volume ◽  
Large Size

The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

Fatigue Properties of Cellulosic-Fiber Mat Reinforced Thermosetting Plastic Composites

2014 ◽  
Author(s):  
Bing Xiao ◽  
Toshihiko Hojo ◽  
Hiroyuki Hamada ◽  
Yuqiu Yang
Keyword(s):  
Natural Fiber ◽  
Low Cycle Fatigue ◽  
Fiber Composite ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Fiber Mats ◽  
Practical Applications ◽  
Cellulosic Fiber ◽  
Synthetic Materials ◽  
Natural Fiber Composite

Natural fiber composite materials are expected as capable materials which may replace the conventional and synthetic materials for the practical applications where manufacture requires less weight and energy conservation. In this study, three kinds of cellulosic-fiber mats including kenaf, bamboo and jute mats were used to fabricate composites by hand lay-up and compression molding methods. As the basic investigation, low cycle fatigue tests were carried out to analyze the material’s fatigue properties by using different bending or tensile loads. Moreover, the scanning electron microscope observation (SEM) on the fracture surfaces has been carried out respectively to investigate the degradation under cycle loads and discuss the possibility of kenaf/bamboo/jute composites achieving hypothetical outstanding mechanical properties in engineering uses.

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