scholarly journals Predicting Continuous Chip to Segmented Chip Transition in Orthogonal Cutting of C45E Steel through Damage Modeling

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 519
Author(s):  
Ashwin Moris Devotta ◽  
P. V. Sivaprasad ◽  
Tomas Beno ◽  
Mahdi Eynian
Keyword(s):  
Flow Stress ◽  
Fracture Initiation ◽  
Material Behavior ◽  
Machining Process ◽  
Dynamic Strain ◽  
Damage Modeling ◽  
Segmented Chip ◽  
First Time ◽  
Strain Model ◽  
Continuous Chip

Machining process modeling has been an active endeavor for more than a century and it has been reported to be able to predict industrially relevant process outcomes. Recent advances in the fundamental understanding of material behavior and material modeling aids in improving the sustainability of industrial machining process. In this work, the flow stress behavior of C45E steel is modeled by modifying the well-known Johnson-Cook model that incorporates the dynamic strain aging (DSA) influence. The modification is based on the Voyiadjis-Abed-Rusinek (VAR) material model approach. The modified JC model provides the possibility for the first time to include DSA influence in chip formation simulations. The transition from continuous to segmented chip for varying rake angle and feed at constant cutting velocity is predicted while using the ductile damage modeling approach with two different fracture initiation strain models (Autenrieth fracture initiation strain model and Karp fracture initiation strain model). The result shows that chip segmentation intensity and frequency is sensitive to fracture initiation strain models. The Autenrieth fracture initiation strain model can predict the transition from continuous to segmented chip qualitatively. The study shows the transition from continuous chip to segmented chip for varying feed rates and rake angles for the first time. The study highlights the need for material testing at strain, strain rate, and temperature prevalent in the machining process for the development of flow stress and fracture models.

scholarly journals Dynamic Plasticity Model for Rapidly Heated 1045 Steel Up to 1000°C

2021 ◽  
Vol 126 ◽  
Author(s):  
Steven P. Mates ◽  
Sheng-Yen Li
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Gaussian Function ◽  
Machining Process ◽  
Dynamic Strain ◽  
Plasticity Model ◽  
Aging Effects ◽  
1045 Steel

The National Institute of Standards and Technology (NIST) developed an experimental technique to measure the dynamic flow stress of metals under rapid heating to study their time-dependent plastic response when heating times are short enough to interrupt or bypass thermally driven microstructural evolution. Such conditions may exist as chips are formed in the machining process. Measurements of American Iron and Steel Institute1045 steel behavior up to 1000 °C showed complex thermal softening due to dynamic strain aging effects and the diffusion-limited austenite transformation process beginning at the A1 temperature (712 °C). This paper proposes a constitutive model to capture the flow stress and hardening evolution of 1045 steel under rapidly heated conditions for simulating metal cutting. The model combines the Preston-Tonks-Wallace plasticity model, which uses five parameters to capture complex rate- and temperature-sensitive strain hardening, with a dual-rate-sensitivity model to capture the response of rapidly heated 1045 steel. Finally, a strain-rate-dependent Gaussian function is introduced to capture dynamic strain aging effects, which act over a narrow range of temperatures that change with strain rate. The proposed model is compared to existing plasticity models for 1045 steel over the range of data available and at a representative machining condition.

Material Behavior Modeling in Machining Simulation of 7075-T651 Aluminum Alloy

2013 ◽  
Vol 136 (1) ◽  
Author(s):  
Shuhui Li ◽  
Bo Hou
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Orthogonal Cutting ◽  
Material Behavior ◽  
Experimental Results ◽  
Machining Process ◽  
Dynamic Flow ◽  
Workpiece Material ◽  
Damage Criterion ◽  
Damage Initiation

Accurate modeling of workpiece material behavior in machining is critical to analyze and design a process. The workpiece material behavior in the machining process involves dynamic flow stress and damage/fracture behavior, which are very difficult to be determined. In this study, the extended split Hopkinson pressure bar (SHPB) test is conducted to determine the dynamic flow stress curves of 7075-T651 aluminum alloy, which enables the strain, strain rate and the temperature obtained in the test to approach that in the cutting condition. A damage criterion under the typical stress state of orthogonal cutting is established to reflect the material damage initiation in primary shear zone. The damage criterion parameters of 7075-T651 alloy are determined by comparing the numerical and experimental results of the proposed inner high-pressure piercing fracture test. The orthogonal cutting test and simulation of 7075-T651 alloy are conducted. It is demonstrated that the determined flow stress and the established damage criterion produces realistic process outputs in agreement with experimental results.

scholarly journals Concurrent material and structure optimization of multiphase hierarchical systems within a continuum micromechanics framework

2021 ◽  
Author(s):  
Tarun Gangwar ◽  
Dominik Schillinger
Keyword(s):  
Optimization Problems ◽  
Computational Cost ◽  
Structure Optimization ◽  
Material Behavior ◽  
Hierarchical Systems ◽  
Material Optimization ◽  
Continuum Micromechanics ◽  
Benchmark Tests ◽  
Constraint Optimization Problems ◽  
First Time

AbstractWe present a concurrent material and structure optimization framework for multiphase hierarchical systems that relies on homogenization estimates based on continuum micromechanics to account for material behavior across many different length scales. We show that the analytical nature of these estimates enables material optimization via a series of inexpensive “discretization-free” constraint optimization problems whose computational cost is independent of the number of hierarchical scales involved. To illustrate the strength of this unique property, we define new benchmark tests with several material scales that for the first time become computationally feasible via our framework. We also outline its potential in engineering applications by reproducing self-optimizing mechanisms in the natural hierarchical system of bamboo culm tissue.

scholarly journals Elasto-thermoviscoplastic finite element analyses of cold upsetting and forging processes of S25C steel with dynamic strain aging considered

2021 ◽  
Vol 2047 (1) ◽  
pp. 012001
Author(s):  
S M Ji ◽  
M K Razali ◽  
K H Lee ◽  
W J Chung ◽  
M S Joun
Keyword(s):  
Finite Element ◽  
Flow Stress ◽  
Dynamic Strain Aging ◽  
Strain Aging ◽  
Large Strain ◽  
Flow Behavior ◽  
Cold Forging ◽  
Dynamic Strain ◽  
Strain Effect ◽  
Strain And Strain Rate

Abstract A practical methodology is presented to characterize the thermoviscoplastic flow stress at larger strain over the temperature range of cold metal forming using tensile and compression tests. Its importance is emphasized for non-isothermal finite element (FE) analysis of automatic multi-stage cold forging (AMSCF) process where maximum strain and strain rate exceed around 3.0 and 200/s, respectively. The experimental compressive flow stress is first characterized using traditional bilinear C-m model with high accuracy. It is employed for describing the closed-form function model to extrapolate the experimental flow stress over the experimentally uncovered ranges of state variables. The strain effect on the flow stress is then improved using the experimental tensile flow stress accurately calculated at large strain and room temperature. A complicated flow behavior of S25C characterized by its dynamic strain aging features is expressed by the presented methodology, which is utilized to analyze the test upsetting and AMSCF processes by the elasto-thermoviscoplastic finite element method for revealing the effects of flow stresses on the process.

A Comparative Study on Hydraulic Bulge Testing and Analysis Methods

2008 ◽  
Author(s):  
Eren Billur ◽  
Muammer Koc¸
Keyword(s):  
Flow Stress ◽  
Optical Measurement ◽  
Measurement Techniques ◽  
Material Behavior ◽  
Biaxial Stress ◽  
Dome Height ◽  
Bulge Test ◽  
Analysis Methods ◽  
Bulge Testing ◽  
Hydraulic Bulge

Hydraulic bulge testing is a material characterization method used as an alternative to tensile testing with the premise of accurately representing the material behavior to higher strain levels (∼70% as appeared to ∼30% in tensile test) in a biaxial stress mode. However, there are some major assumptions (such as continuous hemispherical bulge shape, thinnest point at apex) in hydraulic bulge analyses that lead to uncertainties in the resulting flow stress curves. In this paper, the effect of these assumptions on the accuracy and reliability of flow stress curves is investigated. The goal of this study is to determine the most accurate method for analyzing the data obtained from the bulge testing when continuous and in-line thickness measurement techniques are not available. Specifically, in this study the stress-strain relationships of two different materials (SS201 and Al5754) are obtained based on hydraulic bulge test data using various analysis methods for bulge radius and thickness predictions (e.g., Hill’s, Chakrabarty’s, Panknin’s theories, etc.). The flow stress curves are calculated using pressure and dome height measurements and compared to the actual 3-D strain measurement from a stereo optical and non-contact measurement system ARAMIS. In addition, the flow stress curves obtained from stepwise experiments are compared with the ones from above methods. Our findings indicate that Enikeev’s approach for thickness prediction and Panknin’s approach for bulge radius calculation result in the best agreement with both stepwise experiment results and 3D optical measurement 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.

Plastic Flow Stress and Constitutive Model for H96 Brass Alloy

2015 ◽  
Vol 782 ◽  
pp. 130-136 ◽  
Author(s):  
Ping Zhou ◽  
Wei Guo Guo ◽  
Hai Hui Wu
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
Plastic Flow ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Experimental Results ◽  
Dynamic Strain ◽  
Strain Rates ◽  
Brass Alloy ◽  
Plastic Flow Stress

To explore the thermo-mechanical response of H96 brass alloy, the quasi-static (universal-testing machine) and dynamic (the split Hopkinson pressure bar apparatus) uniaxial compression experiments have been performed under the temperatures from 293 K to 873 K and the strain rates from 0.001 s-1 to 6000 s-1, and the strains over 60% are obtained. Results show that, H96 brass alloy has strong strain hardening behavior, and it becomes weaker with the increasing temperature. In addition, this alloy is sensitive to strain rates; and, it has temperature sensitivity, the dynamic strain aging occurs at the temperature of 473 K and a quasi-static strain rate of 0.001 s-1. Based on the thermal activation dislocation mechanism, paralleled with the experimental results, a plastic flow constitutive model with the physical conception is developed. The model is suitable to predict the plastic flow stress at different temperatures and strain rates. According to comparing results, the model predictions are in good agreement with the experimental results.

scholarly journals Fracture Initiation, Gas Ejection, and Strain Waves Measured on Specimen Surfaces in Model Rock Blasting

2020 ◽  
Author(s):  
Zong-Xian Zhang ◽  
Li Yuan Chi ◽  
Yang Qiao ◽  
De-Feng Hou
Keyword(s):  
High Speed ◽  
Fracture Initiation ◽  
Dynamic Strain ◽  
High Speed Photography ◽  
Surface Cracks ◽  
Rock Blasting ◽  
Measured Velocity ◽  
Strain Waves ◽  
Gas Penetration ◽  
Radial Cracks

AbstractCrack velocity, gas ejection, and stress waves play an important role in determining delay time, designing a blast and understanding the mechanism of rock fragmentation by blasting. In this paper, the emerging times of the earliest cracks and gas ejection on the lateral surfaces of cylindrical granite specimens with a diameter of 240 mm and a length of 300 mm were determined by high-speed photography, and the strain waves measured by an instrument of dynamic strain measurement during model blasting. The results showed that: (1) the measured velocity of gas penetration into the radial cracks was in a range of 196–279 m/s; (2) the measured velocity of a radial crack extending from the blasthole to the specimen surface varied from 489 to 652 m/s; (3) the length of strain waves measured was about 2800 µs, which is approximately 1000 times greater than the detonation time. At about 2850 µs after detonation was initiated, gases were still ejected from the surface cracks, and the specimens still stood at their initial places, although surface cracks had opened widely.

scholarly journals Johnson Cook Material and Failure Model Parameters Estimation of AISI-1045 Medium Carbon Steel for Metal Forming Applications

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 609 ◽  
Author(s):  
Mohanraj Murugesan ◽  
Dong Jung
Keyword(s):  
Flow Stress ◽  
Metal Forming ◽  
Flow Behavior ◽  
Medium Carbon Steel ◽  
Material Behavior ◽  
Model Parameters ◽  
Stress Model ◽  
Medium Carbon ◽  
Aisi 1045 ◽  
Flow Stress Model

Consistent and reasonable characterization of the material behavior under the coupled effects of strain, strain rate and temperature on the material flow stress is remarkably crucial in order to design as well as optimize the process parameters in the metal forming industrial practice. The objective of this work was to formulate an appropriate flow stress model to characterize the flow behavior of AISI-1045 medium carbon steel over a practical range of deformation temperatures (650–950 ∘ C) and strain rates (0.05–1.0 s − 1 ). Subsequently, the Johnson-Cook flow stress model was adopted for modeling and predicting the material flow behavior at elevated temperatures. Furthermore, surrogate models were developed based on the constitutive relations, and the model constants were estimated using the experimental results. As a result, the constitutive flow stress model was formed and the constructed model was examined systematically against experimental data by both numerical and graphical validations. In addition, to predict the material damage behavior, the failure model proposed by Johnson and Cook was used, and to determine the model parameters, seven different specimens, including flat, smooth round bars and pre-notched specimens, were tested at room temperature under quasi strain rate conditions. From the results, it can be seen that the developed model over predicts the material behavior at a low temperature for all strain rates. However, overall, the developed model can produce a fairly accurate and precise estimation of flow behavior with good correlation to the experimental data under high temperature conditions. Furthermore, the damage model parameters estimated in this research can be used to model the metal forming simulations, and valuable prediction results for the work material can be achieved.

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