A calculational model of shear strain and strain rate within shear band in a serrated chip formed during high speed machining

2006 ◽  
Vol 178 (1-3) ◽  
pp. 274-277 ◽  
Author(s):  
C.Z. Duan ◽  
M.J. Wang ◽  
J.Z. Pang ◽  
G.H. Li
Keyword(s):  
Shear Band ◽  
Strain Rate ◽  
Shear Strain ◽  
High Speed ◽  
High Speed Machining ◽  
Serrated Chip ◽  
Strain And Strain Rate

Chip Formation Characteristics in High-Speed Machining of Hardened AISI1045 Steel

2012 ◽  
Vol 565 ◽  
pp. 484-489
Author(s):  
Bing Wang ◽  
Zhan Qiang Liu ◽  
Qi Biao Yang
Keyword(s):  
Shear Band ◽  
Chip Formation ◽  
High Speed ◽  
Adiabatic Shear Band ◽  
Cutting Speed ◽  
Adiabatic Shear ◽  
High Speed Machining ◽  
Micro Hardness ◽  
Serrated Chip ◽  
Aisi1045 Steel

Analyzing mechanism of the chip formation is a significant way to understand the metal cutting process better. The characterization of serrated chip formation in high speed machining of hardened AISI1045 steel is investigated with the aid of optical microscopy and micro-hardness measurement in this paper. The chip morphology evolving from continuous one to serrated one with the cutting speed increasing from 100-1500m/min is observed. Compared with the continuous chip pattern, serrated chip has its particular characterization parameters. The characteristics of serration degree and the segmentation frequency of the serrated chip are presented. The micro-hardness at the adiabatic shear band of serrated chip is then measured. The results show that the serration degree and segmentation frequency of serrated chip have a tendency of enhancement with the cutting speed increasing. The micro-hardness along the adiabatic shear band increases with the cutting speed increasing due to severe strain hardening. With a critical speed at about 100-200m/min, micro-hardness decreases from the tool-chip interface to the free surface of the chip.

Research on Dynamic Constitutive Relation of Materials Taking Account of Damage Evolution and Fracture Law for High Speed Cutting

2011 ◽  
Vol 188 ◽  
pp. 224-229
Author(s):  
J.Q. Li ◽  
Tao Tao Dong ◽  
Min Jie Wang
Keyword(s):  
Shear Band ◽  
Strain Rate ◽  
Constitutive Relation ◽  
Damage Evolution ◽  
High Speed ◽  
Adiabatic Shear Band ◽  
Adiabatic Shear ◽  
Damage Effect ◽  
Serrated Chip ◽  
Softening Effect

The adiabatic shear, which may produce serrated chip, usually occurs for a large number of materials in high speed machining. Adiabatic shear band is an important damage model for metals under high-velocity deformation process. The damage evolution of micro-voids in adiabatic shear bands resulted in material fracture finally. Now the thermal softening effect, the strain rate harding effect and the strain harding effect have been discussed extensively in literature, but there is very little research on its damage effect. Based on the experiments of predecessors, this paper presents a new damage evolution equation that is dependent on strain, strain rate and is suitable for the description of voids damage evolution in adiabatic shear band. The corresponding rate-dependent constitutive relation taking account of damage evolution and temperature are proposed. The predicted results are in good agreement with the experiment datum.

A Modified Johnson–Cook Constitutive Model and Its Application to High Speed Machining of 7050-T7451 Aluminum Alloy

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
Bing Wang ◽  
Zhanqiang Liu ◽  
Qinghua Song ◽  
Yi Wan ◽  
Xiaoping Ren
Keyword(s):  
Aluminum Alloy ◽  
Constitutive Model ◽  
Strain Rate ◽  
Deformation Behavior ◽  
High Speed ◽  
Dynamic Deformation ◽  
Fe Analysis ◽  
High Speed Machining ◽  
Strain And Strain Rate ◽  
Strain Rate Hardening

Constitutive model is the most commonly used method to describe the material deformation behavior during machining process. This paper aims to investigate the material dynamic deformation during high speed machining of 7050-T7451 aluminum alloy with the aid of split Hopkinson pressure bar (SHPB) system and finite element (FE) analysis. First, the quasi static and dynamic compression behaviors of 7050-T7451 aluminum alloy are tested at different loading conditions with a wide range of strain rates (0.001 s, 4000 s, 6000 s, 8000 s, and 12,000 s) and temperatures (room temperature, 100 °C, 200 °C, 300 °C, and 400 °C). The influences of temperature on strain and strain rate hardening effects are revealed based on the flow stress behavior and microstructural alteration of tested specimens. Second, a modified Johnson–Cook (JCM) constitutive model is proposed considering the influence of temperature on strain and strain rate hardening. The prediction accuracies of Johnson–Cook (JC) and JCM constitutive models are compared, which indicates that the predicted flow stresses of JCM model agree better with the experimental results. Then the established JC and JCM models are embedded into FE analysis of orthogonal cutting for 7050-T7451 aluminum alloy. The reliabilities of two material models are evaluated with chip morphology and cutting force as assessment criteria. Finally, the material dynamic deformation behavior during high speed machining and compression test is compared. The research results can help to reveal the dynamic properties of 7050-T7451 aluminum alloy and provide mechanical foundation for FE analysis of high speed machining.

Investigation of the axial compressive behavior of Kevlar fibers using the dynamic loop test

2019 ◽  
Vol 89 (18) ◽  
pp. 3825-3838
Author(s):  
Ahmad Abuobaid ◽  
Raja Ganesh ◽  
John W Gillespie
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Failure Strain ◽  
Kink Band ◽  
Test Method ◽  
Strain Rates ◽  
Compressive Failure ◽  
Band Formation ◽  
Rate Dependent ◽  
Strain And Strain Rate

A dynamic loop test method for measuring strain rate-dependent fiber properties was developed. During dynamic loop testing, the fiber ends are accelerated at constant levels of 20.8, 50 and 343 m/s2. The test method is used to study Kevlar® KM2-600, which fails in axial compression due to kink band formation. The compressive failure strain and strain rate at the onset of kink band formation is calculated from the critical loop diameter ( D C), which is monitored throughout the test using a high-speed camera. The results showed that compressive failure strain increases with strain rates from quasi-static to a maximum strain rate of 116 s−1 by a factor of ∼3. Kink angles (φ) and kink band spacing ( D S) were 60 ° ± 2 ° and 16 ± 3 μm, respectively, over the strain rates tested. Rate-dependent mechanisms of compressive failure by kink band formation were discussed.

VERIFICATION OF THE SHB TEST RESULTS BASED ON THE ONE-DIMENSIONAL STRESS WAVE THEORY

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1068-1073
Author(s):  
TOMOKAZU MASUDA ◽  
KENJI SAITO ◽  
IZUMI MORITA ◽  
SHUSHI IKEDA ◽  
KOICHI MAKII ◽  
...  
Keyword(s):  
Strain Rate ◽  
Stress Wave ◽  
High Speed ◽  
Wave Theory ◽  
High Speed Photography ◽  
Strain Rates ◽  
One Dimensional ◽  
Strain And Strain Rate ◽  
Deformation Behaviors ◽  
The One

In order to evaluate dynamic deformation behaviors under high strain rates, Kobe Steel has developed and applied a Split-Hopkinson Bar (SHB) apparatus. This paper discusses the validity of the strain measurements and strain rates measured by this SHB apparatus. The strain waves that propagated in the incident and transmitted bars and the specimen are captured using a high-resolution type high-speed photography in detail. The strain wave propagated many times in the incident and transmitted bars and the specimen when the specimen was not broken. The amount of the deformation of the specimen decreases with the propagation frequency of the incident wave. On the other hand, to improve accuracy at the strain and strain rate calculated by the one-dimensional stress wave theory, Young's modulus, the longitudinal wave speed, and the density were accurately determined. It was understood that the calculation value showed the strain and strain rate captured with the high-speed photography are a good agreement. As a result, the validity of the measurement accuracy of this SHB could be shown.

scholarly journals Dynamic Shear Characteristic and Fracture Feature of Inconel 690 Alloy under Different High Strain Rates and Temperatures

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Tao-Hsing Chen ◽  
Chih-Kai Tsai ◽  
Te-Hua Fang
Keyword(s):  
Strain Rate ◽  
Shear Strain ◽  
High Strain ◽  
Rate Sensitivity ◽  
Shear Behaviour ◽  
Strain Rates ◽  
Dynamic Shear ◽  
Fracture Feature ◽  
Strain And Strain Rate ◽  
Inconel 690

The high strain shear rate behaviour of Inconel 690 alloy was investigated by using the split Hopkinson torsional bar. The shear strain rates were tested at 900 s−1, 1900 s−1, and 2600 s−1and at temperatures of −100°C, 25°C, and 300°C, respectively. It was found that the dynamic shear behaviour of Inconel 690 alloy was sensitive to strain rate and temperature. The fracture shear strain increased with increasing strain rate and temperature. In addition, the strain rate sensitivity was increased with increasing strain and strain rate but decreased with increasing temperature. Finally, the fracture surfaces were found to contain dimple-like features, and the dimple density increased with increasing strain rate and temperature.

The role of material model in the finite element simulation of high-speed machining of Ti6Al4V

2016 ◽  
Vol 230 (17) ◽  
pp. 2959-2967 ◽  
Author(s):  
Chong-Yang Gao ◽  
Liang-Chi Zhang ◽  
Peng-Hui Liu
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
High Speed ◽  
Material Model ◽  
Machining Process ◽  
High Speed Machining ◽  
Serrated Chip ◽  
Finite Element Program ◽  
Element Simulation ◽  
Improved Model

This paper provides a comprehensive assessment on some commonly used thermo-viscoplastic constitutive models of metallic materials during severe plastic deformation at high-strain rates. An hcp model previously established by us was improved in this paper to enhance its predictability by incorporating the key saturation characteristic of strain hardening. A compensation-based stress-updating algorithm was also developed to introduce the new hcp model into a finite element program. The improved model with the developed algorithm was then applied in finite element simulation to investigate the high-speed machining of Ti6Al4V. It was found that by using different material models, the simulated results of cutting forces, serrated chip morphologies, and residual stresses can be different too and that the improved model proposed in this paper can be applied to simulate the titanium alloy machining process more reliably due to its physical basis when compared with some other empirical Johnson–Cook models.

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