scholarly journals IMPACT OF STRAIN RATE ON MICROALLOYED STEEL SHEET BREAKING

2014 ◽  
Vol 54 (4) ◽  
pp. 281-284 ◽  
Author(s):  
Mária Mihaliková ◽  
Miroslav Német ◽  
Marek Vojtko
Keyword(s):  
Strain Rate ◽  
Steel Sheet ◽  
Loading Rate ◽  
External Factor ◽  
Strength Properties ◽  
Material Behavior ◽  
Material Strength ◽  
Forming Process ◽  
Surface Character ◽  
The Impact

<p>Strain rate is a significant external factor and its influence on material behavior in forming process is a function of its internal structure. The contribution is analysis of the impact of loading rate from 1.6 x 10<sup>-4 </sup>ms<sup>-1</sup> to 24 ms<sup>-1</sup> to changes in the fracture of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from HC420LA grade strips produced by cold rolling and hot dip galvanizing. Material strength properties were compared based on measured values, and changes to fracture surface character were observed.</p>

IF Steel Effect of Rate Deformation on the Fracture Surface Change

2014 ◽  
Vol 635 ◽  
pp. 118-121 ◽  
Author(s):  
Mária Mihaliková ◽  
Miroslav Német ◽  
Marek Vojtko
Keyword(s):  
Fracture Surface ◽  
Steel Sheet ◽  
External Factor ◽  
Strength Properties ◽  
Material Strength ◽  
Interstitial Free ◽  
If Steel ◽  
Material Behaviour ◽  
Forming Process ◽  
Surface Character

Strain rate is a significant external factor and its influence on material behaviour in forming process is a function of its internal structure. In this contribution the influence of loading on the deformation IF steel is investigated using rotate hammer. To study the influence of rate deformation from 8.33 x 10-3 s-1 to 4000 s -1 to changes in the fracture of steel sheet used for bodywork components in cars. Experiments were performed on samples taken from interstitial free (IF) grade strips produced by cold rolling and hot dip galvanizing. Material strength properties were compared based on measured values, and changes to fracture surface character were observed.

Interaction between Crack and Aggregate in Concrete under Dynamic Tensile Loading and Strain-Rate Effect on Material Strength

2011 ◽  
Vol 243-249 ◽  
pp. 5923-5929
Author(s):  
Lu Guang Liu ◽  
Zhuo Cheng Ou ◽  
Zhuo Ping Duan ◽  
Yan Liu ◽  
Feng Lei Huang
Keyword(s):  
Strain Rate ◽  
Loading Rate ◽  
Interfacial Strength ◽  
Aggregate Size ◽  
Tensile Loading ◽  
Strain Rate Effect ◽  
Rate Effect ◽  
Material Strength ◽  
Crack Penetration ◽  
Dynamic Tensile Loading

Crack propagation behaviors at a mortar-aggregate interface in concrete under dynamic tensile loading conditions are investigated numerically. It is found, for a certain interfacial strength and aggregate size, that the crack can penetrate through the interface under an external load with its loading-rate higher than a threshold value. Moreover, for the crack penetration, the smaller the radius of an aggregate, the higher the loading-rate is needed. Therefore, concrete failure energy increase considerably with the loading-rate (or the strain-rate). Such a strain-rate effect on the strength of concrete is in agreement with previous experimental results.

Determining Deformation Behavior of AISI 9310 Steel Varying Temperature and Strain Rate for Aerospace Applications

2021 ◽  
Author(s):  
Adanma Akoma ◽  
Kevin Sala ◽  
Chase Sheeley ◽  
Lesley D. Frame
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
Test Sample ◽  
Material Behavior ◽  
Image Correlation ◽  
Sample Length ◽  
Stress Behavior ◽  
Flow Stress Behavior ◽  
The Impact

Abstract Determination of flow stress behavior of materials is a critical aspect of understanding and predicting behavior of materials during manufacturing and use. However, accurately capturing the flow stress behavior of a material at different strain rates and temperatures can be challenging. Non-uniform deformation and thermal gradients within the test sample make it difficult to match test results directly to constitutive equations that describe the material behavior. In this study, we have tested AISI 9310 steel using a Gleeble 3500 physical simulator and Digital Image Correlation system to capture transient mechanical properties at elevated temperatures (300°C – 600°C) while controlling strain rate (0.01 s-1 to 0.1 s-1). The data presented here illustrate the benefit of capturing non-uniform plastic strain of the test specimens along the sample length, and we characterize the differences between different test modes and the impact of the resulting data that describe the flow stress behavior.

Simulation of Thermally Activated Metal Forming Process With Meso-Scale Crystal Plasticity

2003 ◽  
Author(s):  
Suhui Wang ◽  
Chunlei Xie ◽  
Le Ye ◽  
Xin Wu
Keyword(s):  
Strain Rate ◽  
Crystal Plasticity ◽  
Metal Forming ◽  
High Strain ◽  
Material Behavior ◽  
Slip Systems ◽  
Forming Process ◽  
Forming Simulation ◽  
Thermally Activated ◽  
Von Mises

Under thermally activated deformation conditions many engineering metals (steels, aluminum and magnesium alloys) exhibit much enhanced formability; thus, thermal forming has received increasing interests by automotive industries. The thermally activated material constitutive behaviors are not only strain dependent, but also strain rate and temperature dependent, and it is sensitive to in-situ microstructure evolution. In addition, non-steady-state deformation at a high strain rate (in the order of 10−2s−1 or above) introduces additional challenges in forming simulation. In this case, von Mises based macroscopic plasticity are often not sufficient to describe material behaviors with complex thermomechanical history. In this paper, the rate-dependent crystal plasticity model [1] was applied to the high temperature and high strain rate deformation that is dominated by dislocation creep. A user material subroutine was developed and used for FEA metal forming simulation using commercial ABAQUS/Dynamic code. In the simulation, material behavior was computed based on crystal plasticity at each strain increment without using von-Mises equation or a look-up table of material testing data. By inputting different slip systems or their combinations, and by matching the predicted crystallographic textures with experimentally obtained ones, the active slip systems responsible for the deformation was identified. Then, the material parameters were best fitted to the tensile curves obtained at various strain rates and temperatures. The model was applied for more complex multi-axial metal forming processes. The material behavior, along with its crystallographic texture development, was obtained and validated. As a demonstration, this paper also provides an analysis of a newly developed thrmal forming process [2] with this meso-scale crystal plasticity approach. This forming process involves diameter expansion of a tubular workpiece under combined internal pressure and axial loading and at elevated temperatures.

Refined Modeling of Projectile Impact Onto Submerged Structure

2008 ◽  
Author(s):  
Justin Onisoru ◽  
Ovidiu Coman ◽  
Paul Wilson ◽  
George Thomas
Keyword(s):  
Strain Rate ◽  
Structural Integrity ◽  
Initial Conditions ◽  
Safety Issue ◽  
Constant Strain Rate ◽  
Strain Curve ◽  
Material Behavior ◽  
Spent Fuel ◽  
The Impact

Structural integrity of spent fuel racks is a critical safety issue in nuclear power stations. The standard approach of evaluating the effects of an impact projectile on a submerged structure, which constitute the start point of the current study, involves three main steps: determination of the conditions just prior to the impact (that are considered as initial conditions for the analysis), setting the mechanism of transferring energy from the projectile to the target structure, and determining how that energy is absorbed by the impacted structure. Usually, the dynamics of the projectile are ideally considered, the influence of the fluid presence is restricted to the determination of the impact velocity and strain rate dependency is limited to choosing a true stress vs. strain curve corresponding to some constant strain rate. Starting from the standard engineering approach, the authors have refined the model considering more realistic dynamics of the projectile, extending the influence of the fluid to the entire analysis and using a more accurate strain rate dependant material behavior. Explicit Finite Element analyses are used in order to incorporate the desired effects.

EFFECTS OF STRAIN RATE DEPENDENCY OF MATERIAL PROPERTIES IN LOW VELOCITY IMPACT

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1165-1170 ◽  
Author(s):  
HIROFUMI MINAMOTO ◽  
ROBERT SEIFRIED ◽  
PETER EBERHARD ◽  
SHOZO KAWAMURA
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Yield Stress ◽  
Coefficient Of Restitution ◽  
Finite Element Simulations ◽  
Material Behavior ◽  
Rate Dependency ◽  
Rate Dependent ◽  
Strain Rate Dependency ◽  
The Impact

Impact processes are often analyzed using the coefficient of restitution which represents the kinetic energy loss during impact. In this paper the effect of strain rate dependency of the yield stress on the coefficient of restitution is investigated experimentally and numerically for the impact of a steel sphere against a steel rod. Finite Element simulations using strain-rate dependent material behavior are carried out. In addition, Finite Element simulations with elastic-plastic material behavior, which ignore the strain rate dependency, are carried out as well as elastic material behavior. Comparisons between the experiments and the simulations using strain-rate dependent material behavior show good agreement, and also prove the strong dependency of the coefficient of restitution on the strain rate dependency of the yield stress for steel. The results from both, the experiments and the simulations show also the strong influence of the wave propagation in the rod on the coefficient of restitution.

Viscoplastic Effects Occurring in Impacts of Aluminum and Steel Bodies and Their Influence on the Coefficient of Restitution

2010 ◽  
Vol 77 (4) ◽  
Author(s):  
Robert Seifried ◽  
Hirofumi Minamoto ◽  
Peter Eberhard
Keyword(s):  
Kinetic Energy ◽  
Strain Rate ◽  
Yield Stress ◽  
Split Hopkinson Pressure Bar ◽  
Material Model ◽  
Coefficient Of Restitution ◽  
Material Behavior ◽  
Steel Sphere ◽  
Elastic Plastic ◽  
The Impact

Generally speaking, impacts are events of very short duration and a common problem in machine dynamics. During impact, kinetic energy is lost due to plastic deformation near the contact area and excitation of waves. Macromechanically, these kinetic energy losses are often summarized and expressed by a coefficient of restitution, which is then used for impact treatment in the analysis of the overall motion of machines. Traditionally, the coefficient of restitution has to be roughly estimated or measured by experiments. However, more recently finite element (FE) simulations have been used for its evaluation. Thereby, the micromechanical plastic effects and wave propagation effects must be understood in detail and included in the simulations. The plastic flow, and thus the yield stress of a material, might be independent or dependent of the strain-rate. The first material type is called elastic-plastic and the second type is called elastic-viscoplastic. In this paper, the influence of viscoplasticity of aluminum and steel on the impact process and the consequences for the coefficient of restitution is analyzed. Therefore, longitudinal impacts of an elastic, hardened steel sphere on aluminum AL6060 rods and steel S235 rods are investigated numerically and experimentally. The dynamic material behavior of the specimens is evaluated by split Hopkinson pressure bar tests and a Perzyna-like material model is identified. Then, FE impact simulations and impact experiments with laser-doppler-vibrometers are performed. From these investigations it is shown that strain-rate effects of the yield stress are extremely small for impacts on aluminum but are significant in impacts on steel. In addition, it is demonstrated that it is possible to evaluate for both impact systems the coefficient of restitution numerically, whereas for the aluminum body a simple elastic-plastic material model is sufficient. However, for the steel body an elastic-viscoplastic material model must be included.

Post-Yield Material Characterization for Strain-Based Design

SPE Journal ◽  
2009 ◽  
Vol 14 (01) ◽  
pp. 128-134 ◽  
Author(s):  
Trent M.V. Kaiser
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Heavy Oil ◽  
Material Characterization ◽  
Material Behavior ◽  
Material Strength ◽  
Standard Material ◽  
Strain And Strain Rate ◽  
Static Conditions

Summary Conventional material specifications and test methods were developed to support load-based designs in which inelastic deformations are relatively small and yield strength is the primary material factor governing design. However, in strain-based designs where substantial portions of the structure soften under post-yield deformation, more detailed characterization of the post-yield material behavior is required. This paper presents a framework for describing the post-yield properties of metals (including strain-rate dependence of yield strength) a testing method for measuring post-yield strength in terms of strain and strain rate, and an analytical basis for extrapolating measured properties to static conditions for strain-based design and quality assurance (QA). Introduction Typical test specifications for determining the mechanical properties of oil-country tubular goods (OCTG) were developed to provide an index of mechanical strength to support common load-based design methods. Advancing recovery techniques impose conditions on many well structures that exceed the limits of these methods and the material characterizations on which they are founded. Among these new techniques are those used to recover heavy oil. While typical conditions in heavy-oil reservoirs appear benign, enhanced-oil-recovery (EOR) methods such as thermal stimulation and ultrahigh sand production create some of the most challenging conditions for well structures. Imposed deformations commonly exceed the yield limit of the material, therefore post-yield material characteristics govern much of the structural response. Industry-standard material tests provide only limited characterization of post-yield behavior, particularly at strain levels near the yield point (both pre- and post-yield). Furthermore, test strain rates can affect the measured material strength significantly. Field loading usually occurs at much lower rates and is then sustained for extended periods. A method for characterizing post-yield material properties is, therefore, desired to adequately support designs for such applications. This paper proposes a new basis for characterizing mechanical steel properties that provides the static strength and stiffness over the post-yield strain range. Relaxation characteristics are interpreted from testing, and local stiffness properties are provided. Although static properties are inferred, the test and interpretation basis allows the tests to be executed in a relatively brief time frame, making it possible to apply the method in QA programs to confirm post-yield properties for strain-based designs. A test apparatus built to implement the material-characterization protocol is presented, and sample results are provided to demonstrate the method.

Multisphere Ceramic Composite Concept and its Numerical Study of the Ballistic Response

2011 ◽  
Vol 471-472 ◽  
pp. 1136-1141 ◽  
Author(s):  
Sebastian Stanislawek ◽  
Andrzej Morka ◽  
Tadeusz Niezgoda
Keyword(s):  
Reference Model ◽  
Numerical Study ◽  
Rigid Wall ◽  
Material Behavior ◽  
Material Strength ◽  
Three Dimension ◽  
Sphere Surface ◽  
Convex Shape ◽  
Behavior Simulation ◽  
The Impact

Numerical investigations were performed to determine the influence of the spherical convex shape ceramic - alumina composite in reference to the standard double layer panel. All versions of the target were verified in an impact test including influence upon the position of the AP (Armor Piercing) 7,62x51HHS impact. The crucial parameter which was used for this verification was change in time of the PROJECTILE kinetic energy. The problem has been solved with the usage of the modeling and simulation methods as well as finite elements method implemented in LS-DYNA software. Space discretization for each option was built by three dimension elements guarantying satisfying accuracy of the calculations. For material behavior simulation specific models including the influence of the strain rate and temperature changes were considered. Projectile’s core made of HHS and aluminum plate material were described by Johnson-Cook model and ceramic target with Johnson-Holmquist model. In the studied panels the area surrounding back edges was supported by rigid wall. The obtained results show interesting properties of the new structures considering their ballistic resistance. However only certain places were chosen for tests, the protection ability against projectile attack is in general higher than the reference model. What is particularly interesting during the 6.6mm from the sphere center impact the sphere surface trajectory deviation effect is present. A projectile is not stopped here by material strength but the front layer shape. Moreover it can be assumed that this phenomenon will take place on majority of points on the sphere surface. Despite this fact, a ceramic multi sphere layer is less susceptible to overall destruction, depending on the impact point. The results of those numerical simulations can be used for designing of modern armor protection systems against hard kinetic projectiles.

scholarly journals Sequential Processing of Cold Gas Sprayed Alloys by Milling and Deep Rolling

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3699
Author(s):  
Daniel Meyer ◽  
Lars Schönemann ◽  
Nicole Mensching ◽  
Volker Uhlenwinkel ◽  
Bernhard Karpuschewski
Keyword(s):  
Deposition Process ◽  
Material Behavior ◽  
Material Composition ◽  
Deep Rolling ◽  
Forming Process ◽  
Material Deposition ◽  
Particle Bonding ◽  
Future Work ◽  
The Impact ◽  
Cold Gas

Cold gas spraying (CS) is a solid-state material deposition process which, in addition to the flexible repair of individual component areas, also enables the build-up of larger samples. The layers are created on a substrate by the impact-induced bonding of highly accelerated micrometer particles. Since melting does not occur, the material composition can be varied flexibly and independently of material-specific melting points. In this work, the influence of the described forming process on subsequent machining by milling and deep rolling is investigated. The process forces measured during milling and the surface topography after milling and deep rolling were influenced by the material composition and the CS-related properties, e.g., high material hardness or particle bonding. In contrast to prior assumptions, deep rolling was shown to have no influence on the determined hardness depth profile for the investigated materials. Future work will focus on additional analyses, such as the determination of half-widths, to obtain further insight on the material behavior.

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