On the Microstructural Characteristics of UFG Microalloyed Steel Influencing the Mechanical Behavior under Dynamic Loading

2018 ◽  
Vol 941 ◽  
pp. 39-45 ◽  
Author(s):  
Janusz Majta ◽  
Remigiusz Bloniarz ◽  
Marcin Kwiecień ◽  
Krzysztof Muszka
Keyword(s):  
Strain Rate ◽  
Mechanical Behavior ◽  
Dynamic Loading ◽  
Work Hardening ◽  
Mechanical Response ◽  
Thermomechanical Processing ◽  
Microalloyed Steel ◽  
Material Behavior ◽  
Second Phase ◽  
Loading Conditions

This paper presents a summary of a preliminary research aimed at producing ultrafine-grained (UFG) and heterogeneous microstructure in microalloyed steel and testing these materials under dynamic loading conditions (strain rates 800 s-1 and 1800s-1). The UFG and bimodal-structures, due to grain size, structural composition or morphology of structural components, were produced by an advanced thermomechanical processing, namely rolling in: hot, two-phase and cold-hot combined conditions. The advantage of bimodal microstructures is their maximization of mechanical behavior under extreme loading conditions due to promoted accumulation and interactions of geometrically necessary dislocations. The dynamic work-hardening behavior has been studied as a function of solute atoms and fine-scale, second-phase particles in the UFG and bimodal-structures. The substantial complexity of the phenomena, which occur through the evolution of microstructure and texture in response to dynamic loading, presents formidable challenges to theoretical model development of plastic deformation of UFG and bimodal-structures. Such an extraordinary work hardening provides an attractive strategy to develop optimal combination of mechanical properties i.e. strength/ductility ratio. A multi-scale analysis capable of including material behavior in different scales should be applied to discuss mechanical response of mentioned above microstructures and to help to analyze their influence on mechanical behavior under dynamic loading. The investigation was performed for a material of common application: high strength microalloyed steel X70. The experimental results show that strain rate sensitivity of the heterogeneous microstructures obtained by various thermomechanical rolling routes are significant, but not by a similar magnitude with the microstructure compositions and increasing strain rate.

scholarly journals Modeling the Mechanical Response of Auxetic Metamaterials to Dynamic Effects

2021 ◽  
pp. 144-152
Author(s):  
V. V Skripnyak ◽  
M. O Chirkov ◽  
V. A Skripnyak
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Relative Density ◽  
Dynamic Loading ◽  
Uniaxial Compression ◽  
Mechanical Response ◽  
Effective Strain ◽  
Absorbed Energy ◽  
Auxetic Structure

The paper investigates the mechanical response of a 3D auxetic structure created on the basis of a unit cell with pre-buckled structural elements to dynamic loading. The aim of the work is to study deformations of the auxetic structure made of an alpha titanium alloy during uniaxial compression at 100 m/s, to evaluate dissipative properties of the structure during high-speed deformation, and to estimate the characteristic time of the metamaterial’s compaction with a relative density of 0.0115. The numerical simulation of the metamaterial at effective strain rate of 2000 1/s has been performed using LS DYNA solver. To describe the mechanical behavior of the titanium alloy in frame elements, we use a model of an elastic-plastic damaged medium, which takes into account the strain rate sensitivity of the plastic flow, temperature changes due to dissipative effects, and the effect of the stress state triaxiality parameter on nucleation and growth of structural damages. The numerical studies have shown that the auxetic effect in the studied metamaterial is retained under high-rate elastoplastic deformation. At a speed of the uniaxial compression of 100 m/s, deformation in the volume of the metamaterial proceeds nonuniformly. Under dynamic loading of the considered auxetic metamaterial, the deformation and fracture modes depend not only on the parameters of the cell geometry, but also on the mechanical behavior of the framework material, as well as on the relative density. This makes it possible to control the deformations of the cells under mechanical stress. Layers of compacted cells are formed near the dynamic loading surface. The instability of the cells of the auxetic metamaterials increases the absorbed energy. The calculated value of the specific absorbed energy under dynamic uniaxial compression reaches 3.4 kJ/kg, and is comparable with the values for frame structures made of Ti-6Al-4V with an equivalent specific mass density. The results indicate the possibility of creating protective structures using auxetic cellular structures on the base of the pre-buckled elements of the rolled metal.

scholarly journals How the Thermomechanical Processing Can Modify the High Strain Rate Mechanical Response of a Microalloyed Steel

Materials ◽  
2021 ◽  
Vol 14 (20) ◽  
pp. 6062
Author(s):  
Remigiusz Błoniarz ◽  
Janusz Majta ◽  
Bogdan Rutkowski ◽  
Grzegorz Korpała ◽  
Ulrich Prahl ◽  
...  
Keyword(s):  
Dynamic Loading ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Thermomechanical Processing ◽  
Microstructural Analysis ◽  
Image Correlation ◽  
Microalloyed Steels ◽  
Loading Conditions ◽  
Hopkinson Pressure Bar ◽  
Dynamic Loading Conditions

The effects of thermomechanical processing (TMP) on the mechanical response of microalloyed steels subjected to dynamic loading conditions were examined. The deformation conditions in the thermomechanical laboratory rolling processes were selected on the basis of dilatometric tests. It allowed (with a constant value of total deformation) us to obtain microstructures with different compositions and morphology of the particular components. Several samples characterized by a particularly complex and unexpected representation of the obtained microstructures were selected for further research. Plastometric tests, i.e., compression and tensile tests, were performed under quasi-static loading with digital image correlation (DIC) analysis, and under dynamic loading on the Split Hopkinson Pressure Bar (SHPB) apparatus with strain rates of 1400 and 2000 s−1. Samples deformed in such conditions were subjected to microstructural analysis and hardness measurements. It has been observed that the use of various combinations of TMP parameters can result in the formation of specific microstructures, which in turn are the source of an attractive mechanical response under dynamic loading conditions. This opens up new possible areas of application for such popular structural materials which are microalloyed steels.

Mechanical Characterization of Assemblies Bonded With Pressure-Sensitive Adhesives (PSAs)

2015 ◽  
Author(s):  
Hao Huang ◽  
Abhijit Dasgupta ◽  
Ehsan Mirbagheri ◽  
Srini Boddapati
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Mechanical Characterization ◽  
Bonding Temperature ◽  
Process Conditions ◽  
Second Phase ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Behavior ◽  
Pressure Sensitive

The focus of this paper is on the stress-strain behavior and creep response of a pressure-sensitive adhesive (PSA) with and without carrier layers. This study consists of two phases. The first phase focuses on understanding of the effects of fabrication profiles, including bonding pressure, bonding temperature, bonding time, and aging time, on the PSA joint strength. This part of the study is used to identify an acceptable bonding and aging conditions for manufacturing a robust PSA bonded assembly. Specimens fabricated with this selected set of bonding process conditions are then used for mechanical characterization. The second phase focuses on the assembly’s mechanical behavior (stress-strain behavior and the creep curves) under different loading conditions, including loading stress, loading rate, and loading temperature. The mechanical behavior of PSA bonded assemblies is affected not only by the loading conditions, but also by the assembly architecture. The mechanical behaviors and failure modes of PSAs with and without carrier layers are compared. The reasons for these differences are also discussed.

Effect of Structure on Response of a Three-Dimensional-Printed Photopolymer-Particulate Composite Under Intermediate Strain Rate Loading

2020 ◽  
Vol 87 (11) ◽  
Author(s):  
Amirreza Keyhani ◽  
Min Zhou
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Local Heating ◽  
Three Dimensional ◽  
Particulate Composite ◽  
Deformation Energy ◽  
Material Behavior ◽  
Localized Deformation ◽  
Failure Initiation ◽  
Lagrangian Finite Element

Abstract The thermo-mechanical response of an additively manufactured photopolymer-particulate composite under conditions of macroscopic uniaxial compression without lateral confinement at overall strain rates of 400–2000 s−1 is studied. The material has a direct-ink-written unidirectional structure. Computations are performed to quantify the effects of microstructure attributes including anisotropy, defects, and filament size on localized deformation, energy dissipations, and temperature rises. To this effect, an experimentally informed Lagrangian finite element framework is used, accounting for finite-strain elastic–plastic deformation, strain-rate effect, failure initiation and propagation, post-failure internal contact and friction, heat generation due to friction and inelastic bulk deformation, and heat conduction. The analysis focuses on the material behavior under overall compression. Despite relatively low contribution to overall heating, friction is localized at fracture sites and plays an essential role in the development of local temperature spikes unknown as hotspots. The microstructural attributes are found to significantly affect the development of the hotspots, with local heating most pronounced when loading is transverse to the filaments or when the material has higher porosities, stronger inter-filament junctions, or smaller filament sizes. Samples with smaller filament sizes undergo more damage, exhibit higher frictional dissipation, and develop larger hotspots that occur primarily at failure sites.

Changing the Hardness Automotive Steels at Different Strain Rate

2014 ◽  
Vol 635 ◽  
pp. 41-44
Author(s):  
Miroslav Német ◽  
Mária Mihaliková ◽  
Alexandra Kovalčíkova ◽  
Anna Lišková
Keyword(s):  
Strain Rate ◽  
Dynamic Loading ◽  
Automotive Industry ◽  
Interstitial Free ◽  
Loading Conditions ◽  
Product Testing ◽  
Dynamic Conditions ◽  
Interstitial Free Steel ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading

Currently, the automotive industry used sheets of different qualities. The most common include IF (inter Interstitial Free) steel and alloyed steel. Use the sheet quality depends on the point of application in the production car. Testing and product testing is a standard part of the process of innovation and production itself. Testing of automotive steels under dynamic conditions is increasingly important. Changing the hardness HV 1 was performed on the fractured bars on the static and dynamic loading conditions. Tests were made on steel IF and S 460.

Evaluation of Friction at High Strain Rate using the Split Hopkinson Bar

2015 ◽  
Vol 651-653 ◽  
pp. 108-113 ◽  
Author(s):  
Archimede Forcellese ◽  
Edoardo Mancini ◽  
Marco Sasso ◽  
Michela Simoncini
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Dynamic Loading ◽  
High Strain ◽  
Outer Diameter ◽  
Loading Conditions ◽  
Split Hopkinson ◽  
Dynamic Loading Conditions ◽  
Static And Dynamic Loading ◽  
Frictional Behaviour

The present work aims at studying the influence of strain rate on the frictional behaviour of AA7075 aluminium alloy in the O-annealed temper state. To this purpose, ring compression tests were performed both under quasi-static and dynamic loading conditions. The high strain rate tests were carried out by means of the Split Hopkinson Tension-Compression Bar in the direct version. In both cases, hollow cylindrical samples, characterised by an initial outer diameter to inner diameter to height ratio of 6:3:2, were tested under dry condition and by lubricating with molybdenum disulphide grease. The different frictional behaviour exhibited by AA7075-O under quasi-static and dynamic loading conditions can be attributed to the strain rate effect both on the plastic flow behaviour of the deformed material, and on the thickness of the lubricant film.

Mesoscale Analysis of Porous Shape Memory Alloys

2000 ◽  
Author(s):  
Virginia G. DeGiorgi ◽  
Muhammad A. Qidwai
Keyword(s):  
Shape Memory Alloys ◽  
Shape Memory ◽  
Dynamic Loading ◽  
Smart Materials ◽  
Bulk Material ◽  
Material Behavior ◽  
Loading Conditions ◽  
Shape Variation ◽  
Energy Absorbing ◽  
Dynamic Loading Conditions

Abstract Shape memory alloys are frequently used in smart materials and structures as the active component. Their ability to provide high force and large displacements has been used to the advantage in many applications. The majority of applications to date utilize solid shape memory alloy materials in quasi-static loading conditions. Recent work has proposed the use of porous SMAs as an energy absorbing material under dynamic loading conditions. The use of porous SMAs under dynamic loading will require advancements in the understanding of SMA behavior both in the dense or solid form and in the porous form. The current work examines the quasi-static behavior of porous SMA as a first step. The material behavior is modeled on a mesoscale level allowing for the examination of pore size and shape variation effects. Bulk material response is estimated and compared with micromechanical periodic unit cell predictions.

scholarly journals The mechanical response of UFG and nanostructured microalloyed steels subjected to dynamic loading conditions

2018 ◽  
Vol 183 ◽  
pp. 03019
Author(s):  
Remigiusz Bloniarz ◽  
Janusz Majta ◽  
Carl P. Trujillo ◽  
Ellen K. Cerreta
Keyword(s):  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
Thermomechanical Processing ◽  
High Strength Steels ◽  
High Strength ◽  
Microalloyed Steels ◽  
Large Strains ◽  
Loading Conditions ◽  
Hopkinson Pressure Bar ◽  
Pressure Bar

As the number of available, advanced high-strength metallic materials possibilities increases due to advancements in processing (for example advanced thermomechanical processing - ATP or severe plastic deformation - SPD), experimental comparisons alone are not sufficient for determination of the most ideal microstructures for specific applications. Our study deals with the dynamic behaviour of high strength steels and in particular with ultrafine-grained (UFG) microalloyed ferrite and austenite. The forming processes of modern UFG materials require rheological models describing the materials behaviour at large strains and strain rates up to over 1000 s-1. In our case, the mechanical response of UFG steels (produced using MaxStrain system) was investigated with split Hopkinson pressure bar (SHPB) tests, performed at room temperature. The dynamic work-hardening behaviour as a function of solute atoms and fine-scale, secondphase particles in the nano-structures of microalloyed ferrite and austenite has been compared to the mechanical response of these materials under quasi-static loading conditions.

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