scholarly journals Variation of Relief Topography and Hardness of Surface Layers of Materials Due to Impact-Oscillatory Loading

Materials ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 2720
Author(s):  
Mykola Chausov ◽  
Pavlo Maruschak ◽  
Andrii Pylypenko ◽  
Janette Brezinová ◽  
Roman Bishchak ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Base Metal ◽  
Dissipative Structures ◽  
Roughness Parameters ◽  
Surface Layers ◽  
Flat Surfaces ◽  
Equilibrium Processes ◽  
Plastic Materials ◽  
Orderly System

It was shown previously that cyclic loading can be used to extend the fatigue life of sheet plastic materials subjected to the preliminary impact-oscillatory loading. This type of loading causes dynamic non-equilibrium processes (DNP) in materials, which lead to the formation of dissipative structures in materials and on their surface. The density of these dissipative structures is less than that of the base metal. In this paper, the results of investigations into the relief and hardness of surface layers modified by impact-oscillatory loading are analyzed on the example of five structural materials. The signs of a regular, orderly system of microextrusions formed on flat surfaces of all materials due to DNP are considered along with the alignment of roughness parameters Rz and Ra of relief profiles. The effect of impact-oscillatory loading is one of the main causes that lead to the extension of the fatigue life of materials.

Fatigue Life Improvement of Welded Elements and Structures by Ultrasonic Impact Treatment

2011 ◽  
Author(s):  
Yuriy Kudryavtsev ◽  
Jacob Kleiman
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Fatigue Strength ◽  
Residual Stresses ◽  
Fatigue Testing ◽  
Highway Bridges ◽  
Surface Layers ◽  
Ultrasonic Impact Treatment ◽  
Stress Relieving ◽  
Life Improvement

The ultrasonic impact treatment (UIT) is relatively new and promising process for fatigue life improvement of welded elements and structures. In most industrial applications this process is known as ultrasonic peening (UP). The beneficial effect of UIT/UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of a material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material. The UP technique is based on the combined effect of high frequency impacts of special strikers and ultrasonic oscillations in treated material. Fatigue testing of welded specimens showed that UP is the most efficient improvement treatment as compared with traditional techniques such as grinding, TIG-dressing, heat treatment, hammer peening and application of LTT electrodes. The developed computerized complex for UP was successfully applied for increasing the fatigue life and corrosion resistance of welded elements, elimination of distortions caused by welding and other technological processes, residual stress relieving, increasing of the hardness of the surface of materials. The UP could be effectively applied for fatigue life improvement during manufacturing, rehabilitation and repair of welded elements and structures. The areas/industries where the UP process was applied successfully include: Shipbuilding, Railway and Highway Bridges, Construction Equipment, Mining, Automotive, Aerospace. The results of fatigue testing of welded elements in as-welded condition and after application of UP are considered in this paper. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increasing of fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used.

scholarly journals Structural and mechanical defects of materials of offshore and onshore main gas pipelines after long-term operation

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Pavlo Maruschak ◽  
Sergey Panin ◽  
Iryna Danyliuk ◽  
Lyubomyr Poberezhnyi ◽  
Taras Pyrig ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Quantitative Analysis ◽  
Stress Concentration ◽  
Cyclic Loading ◽  
Fatigue Cracks ◽  
Preliminary Deformation ◽  
Term Operation ◽  
Steel Pipes

AbstractThe study has established the main regularities of a fatigue failure of offshore gas steel pipes installed using S-lay and J-lay methods.We have numerically analyzed the influence of preliminary deformation on the fatigue life of 09Mn2Si steel at different amplitudes of cyclic loading. The results have revealed the regularities of formation and development of a fatigue crack in 17Mn1Si steel after 40 years of underground operation. The quantitative analysis describes the regularities of occurrence and growth of fatigue cracks in the presence of a stress concentration.

scholarly journals Influence of the microstructure on the cyclic stress-strain behaviour and fatigue life in hypo-eutectic Al-Si-Mg cast alloys

2018 ◽  
Vol 165 ◽  
pp. 15004 ◽  
Author(s):  
Jochen Tenkamp ◽  
Alexander Koch ◽  
Stephan Knorre ◽  
Ulrich Krupp ◽  
Wilhelm Michels ◽  
...  
Keyword(s):  
Solid Solution ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Weight Ratio ◽  
Cyclic Stress ◽  
Stress Strain ◽  
Strain Behaviour ◽  
Eutectic Morphology ◽  
Cast Alloys ◽  
Incremental Step

Aluminium alloys are promising candidates for energy-and cost-efficient components in automotive and aerospace industries, due to their excellent strength-to-weight ratio and relatively low cost compared to titanium alloys. As modern cast processing and post-processing, e.g. hot isostatic pressing, result in decreased frequency and size of defects, the weakest link depends on microstructural characteristics, e.g. secondary dendrite arm spacing (SDAS), Si eutectic morphology and α-Al solid solution hardness. Hereby, fatigue investigations of the effect of the microstructure characteristics on the cyclic stress-strain behaviour as well as fatigue mechanisms in the low cycle and high cycle fatigue regime are performed. For this purpose, samples of the aluminium cast alloy EN AC-AlSi7Mg0.3 with different Si eutectic morphology and α-Al solid solution hardness were investigated. To compare the monotonic and cyclic stress-strain curves, quasistatic tensile tests and incremental step tests were performed on two microstructure conditions. The results show that the cyclic loading leads to a hardening of the material compared to monotonic loading. Based on damage parameter Woehler curves, it is possible to predict the damage progression and fatigue life for monotonic and cyclic loading in hypo-eutectic Al-Si-Mg cast alloys by one power law.

The Structure and Mechanical Properties of VT23 Welded Joints with Surface Layer Modified by Ultrasonic Mechanical Forging

2017 ◽  
Vol 743 ◽  
pp. 264-268 ◽  
Author(s):  
Anastasia Smirnova ◽  
Yury Pochivalov ◽  
Victor Panin ◽  
Anatoly Orishich ◽  
Aleksandr Malikov ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
Fatigue Life ◽  
Welded Joints ◽  
Experimental Tests ◽  
Relaxation Property ◽  
Surface Layers ◽  
Β Phase ◽  
Fatigue Life Test ◽  
Vt23 Titanium Alloy

The structure and mechanical properties of welded joints of VT23 titanium alloy received by method of laser welding after modifying the surface layers by ultrasonic mechanical forging (Treatment 1 and Treatment 2) were investigated. The experimental tests have revealed that the Treatment 2 provides a multiple increase in the relaxation property in fatigue life test. The formation of nonuniform distribution of vanadium, chromium and molybdenum in the welded joint increases the strength and, at the same time, the brittleness of β-phase. Mechanical treatment of the surface layers in the second mode provides a multiple increase in ductility up to 13%, in the as-received condition up to 9.9%. In consequence of plastic deformation, the β-phase intensity reduces twice with Treatment 2 which is related to its clustering. As follows from a presented data, the fatigue life of the VT23 titanium alloy has increased more than threefold.

scholarly journals Bone-Inspired Microarchitectured Materials with Enhanced Fatigue Life

2018 ◽  
Author(s):  
Ashley M. Torres ◽  
Adwait A. Trikanad ◽  
Cameron A. Aubin ◽  
Floor M. Lambers ◽  
Marysol Luna ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Cyclic Loading ◽  
Energy Absorption ◽  
Fatigue Failure ◽  
Cancellous Bone ◽  
Axial Stiffness ◽  
High Porosity ◽  
Preferred Direction ◽  
Naturally Occurring ◽  
Apparent Stiffness

Microarchitectured materials achieve superior mechanical properties through geometry rather than composition 1-4. Although lightweight, high-porosity microarchitectured materials can have high stiffness and strength, stress concentrations within the microstructure can cause flaw intolerance under cyclic loading 5,6, limiting fatigue life. However, it is not known how microarchitecture contributes to fatigue life. Naturally occurring materials can display exceptional mechanical performance and are useful models for the design of microarchitectured materials 7,8. Cancellous bone is a naturally occurring microarchitectured material that often survives decades of habitual cyclic loading without failure. Here we show that resistance to fatigue failure in cancellous bone is sensitive to the proportion of material oriented transverse to applied loads – a 30% increase in density caused by thickening transversely oriented struts increases fatigue life by 10-100 times. This finding is surprising in that transversely oriented struts have negligible effects on axial stiffness, strength and energy absorption. The effects of transversely oriented material on fatigue life are also present in synthetic lattice microstructures. In both cancellous bone and synthetic microarchitectures, the fatigue life can be predicted using the applied cyclic stress after adjustment for apparent stiffness and the proportion of the microstructure oriented transverse to applied loading. In the design of microarchitectured materials, stiffness, strength and energy absorption is often enhanced by aligning the microstructure in a preferred direction. Our findings show that introduction of such anisotropy, by reducing the amount of material oriented transverse to loading, comes at the cost of reduced fatigue life. Fatigue failure of durable devices and components generates substantial economic costs associated with repair and replacement. As advancements in additive manufacturing expand the use of microarchitectured materials to reusable devices including aerospace applications, it is increasingly necessary to balance the need for fatigue life with those of strength and density.

Elastic-Plastic Finite Element Simulation and Fatigue Life Prediction for Beam and Elbow Under Cyclic Loading

2007 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Brian N. Leis
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Plastic Strain ◽  
Kinematic Hardening ◽  
Kinematic Model ◽  
Cyclic Plastic ◽  
Hardening Models ◽  
Critical Location ◽  
Cyclic Plastic Strain

Work hardening and Bauschinger effects on plastic deformation and fatigue life for a beam and an elbow under cyclic loading are examined using finite element analysis (FEA). Three typical material plastic hardening models, i.e. isotropic, kinematic and combined isotropic/kinematic hardening models are adopted in the FEA calculations. Based on the FEA results of cyclic stress and strain at a critical location and using an energy-based fatigue damage parameter, the fatigue lives are predicted for the beam and elbow. The results show that (1) the three material hardening models determine similar stress at the critical location with small differences during the cyclic loading, (2) the isotropic model underestimates the cyclic plastic strain and overestimates the fatigue life, (3) the kinematic model overestimates the cyclic plastic strain and underestimates the fatigue life, and (4) the combined model predicts the intermediate cyclic plastic strain and reasonable fatigue life.

The Research Status of Titanium Clad Steel

2014 ◽  
Vol 941-944 ◽  
pp. 187-192
Author(s):  
Jia Geng Liu ◽  
Jing Tao Han ◽  
Jing Liu ◽  
Shuai Ji
Keyword(s):  
Base Metal ◽  
Explosive Welding ◽  
Surface Layers ◽  
Roll Bonding ◽  
Research Status ◽  
Cold Roll ◽  
Cold Roll Bonding ◽  
New Ideas ◽  
Clad Steel ◽  
Atom Bond

The main methods for manufacturing titanium clad steel are described, also the mechanisms of cold roll bonding and explosive welding are specifically analyzed. It is showed that two opposing brittle surface layers produced by scratch brushing break up and underlying base metal is extruded through cracks of the broken layers and creates an atom-to-atom bond for cold roll bonding, however, a lot of parameters affect the bonding for explosive welding. Some new ideas for manufacturing titanium clad steel is discussed herein.

Stiffness Degradation of Digital Polypropylene Under Fatigue Loading: Investigations via 3-Dimensional Polyjet Printed Coupons

2020 ◽  
Author(s):  
Ravi Pratap Singh Tomar ◽  
Furkan I. Ulu ◽  
Ajit Kelkar ◽  
Ram V. Mohan
Keyword(s):  
Experimental Data ◽  
Regression Analysis ◽  
Fatigue Life ◽  
Cyclic Loading ◽  
Fatigue Loading ◽  
Stiffness Degradation ◽  
Damage State ◽  
3 Dimensional ◽  
Accumulated Damage ◽  
Polyjet Printing

Abstract The utilization of additively manufactured parts is gaining popularity in functional applications. Polymer-based additive manufacturing (AM) parts are utilized in a variety of engineering applications for automotive, aerospace, and energy. AM printed parts are however newer class of materials, and structural performance of these materials is not fully understood completely, and very limited exists currently on precisely performance of Polyjet printed parts and associated digital materials under fatigue loading. This paper investigates the stiffness degradation under tension-tension fatigue loading of digital polypropylene using homogenous 3-Dimensional test coupons formed using PolyJet printing. Homogeneous 3-Dimensional test configuration employed in the present study eliminates the process-induced limitations of traditional ASTM D638 2D fatigue test coupons for AM processed materials. Fatigue data is analyzed to present an empirical model of effective elastic modulus and an analytical model of the accumulated damage state, as defined on the basis of stiffness degradation during cyclic loading. Further, the actual damage accumulation due to cyclic loading with the predicted model is compared. Modeling of the S-N diagram provides a better estimation of fatigue life and fatigue life modeling of AM printed test coupons and is obtained via linear regression analysis of experimental data with high correlation coefficient R2 (0.9971). The analytical model of the accumulated damage state is based on the stiffness degradation and is derived from the regression analysis of experimental data of stiffness degradation at different loading percentages assuming a polynomial of degree 4. Present study provides insight into the fatigue damage state and cyclic performance of digital polypropylene from Polyjet printing.

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