Correlation of Flow Stress With Strain Rate and Temperature During Machining

1973 ◽  
Vol 95 (2) ◽  
pp. 94-98 ◽  
Author(s):  
J. A. Bailey ◽  
D. G. Bhanvadia
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Metal Cutting ◽  
Strain Rates ◽  
Rake Face ◽  
Rate Parameter ◽  
Idealized Model ◽  
Orthogonal Metal Cutting ◽  
Continuous Chip ◽  
Strain Rate Parameter

An idealized model of the orthogonal metal cutting process is used to determine the stresses, strain rates, and temperatures at the tool rake face for the machining of several materials under dry, unlubricated conditions, where a continuous chip is produced with an absence of a built-up edge. An attempt is made to correlate stress with strain rate and temperature using a temperature compensated strain rate parameter, and velocity modified temperature.

Medium to High Strain-Rate Characterization of Lead Free Solder Alloys Through Metal Cutting Experiments

2019 ◽  
Author(s):  
Yuvraj Singh ◽  
Anirudh Udupa ◽  
Srinivasan Chandrasekar ◽  
Ganesh Subbarayan
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Metal Cutting ◽  
High Strain ◽  
Lead Free ◽  
Strain Rates ◽  
Lead Free Solder ◽  
Orthogonal Metal Cutting ◽  
Free Solder

Abstract Studies on medium to high strain-rate characterization (≥ 0.1s−1) of lead-free solder are relatively few, primarily due to the lack of available methods for testing. Prior work in literature uses Split Hopkinson Bar (SPHB) experiments for high strain-rate characterization (≥ 300s−1) [1,2], while a modified micro-scale tester is used for medium strain-rate characterization (0.005s−1 to 300s−1) [3] and an impact hammer test setup for testing in a strain-rate regime from 1s−1 to 100s−1 [4]. However, there is still limited data in strain-rate regimes of relevance, specifically for drop shock applications. In this paper, we present orthogonal metal cutting as a novel method to characterize lead-free solder alloys. Experiments are carried out using a wedgelike tool that cuts through a work piece at a fixed depth and rake angle while maintaining a constant cutting velocity. These experiments are conducted at room temperature on Sn1.0Ag0.5Cu bulk test specimens with strain-rates varying from 0.32 to 48s−1. The range of strain-rates is only limited by the ball screw driven slide allowing higher strain-rates if needed. The strains and strain-rates are captured through Particle Image Velocimetry (PIV) using sequential images taken from a high-speed camera just ahead of the cutting tool. The PIV enables non-contact recording of high strain-rate deformations, while the dynamometer on the cutting head allows one to capture the forces exerted during the cutting process. Results for the stress-strain response obtained through the experiments are compared to prior work for validation. Orthogonal metal cutting is shown to be a potentially attractive method for characterization of solder at higher strain-rates.

Effects of Strain Rate and Temperature in Orthogonal Metal Cutting

1966 ◽  
Vol 8 (3) ◽  
pp. 264-275 ◽  
Author(s):  
G. Boothroyd ◽  
J. A. Bailey
Keyword(s):  
Theoretical Analysis ◽  
Strain Rate ◽  
Metal Cutting ◽  
Single Phase ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Rake Angle ◽  
Cutting Process ◽  
Strain Rates ◽  
Continuous Chip

A new theoretical analysis of the orthogonal cutting process is described which is based on the known behaviour of a single phase metal at high strains, strain rates and temperatures. The theoretical analysis applies to the case where a continuous chip is produced under non-lubricated conditions with the absence of a built-up edge on the tool face and indicates the important parameters in the cutting process. The theory is examined experimentally and its validity established. Finally, from a knowledge of the effects of strain rate and temperature on the yield stress of a single phase metal, the theory is used to predict the effects of changes in cutting speed and tool rake angle on the tool forces and geometry of the cutting process. These predictions are compared qualitatively with the results of cutting tests.

Comparative Study of the Dynamic Behavior of AA2519 Aluminum Alloy in T6 and T8 Temper Conditions

2019 ◽  
Author(s):  
Adewale Olasumboye ◽  
Gbadebo Owolabi ◽  
Olufemi Koya ◽  
Horace Whitworth ◽  
Nadir Yilmaz
Keyword(s):  
Plastic Deformation ◽  
Aluminum Alloy ◽  
Stress Response ◽  
Flow Stress ◽  
Yield Strength ◽  
Strain Rate ◽  
High Strain ◽  
Second Phase ◽  
Strain Rates ◽  
High Strain Rates

Abstract This study investigates the dynamic response of AA2519 aluminum alloy in T6 temper condition during plastic deformation at high strain rates. The aim was to determine how the T6 temper condition affects the flow stress response, strength properties and microstructural morphologies of the alloy when impacted under compression at high strain rates. The specimens (with aspect ratio, L/D = 0.8) of the as-cast alloy used were received in the T8 temper condition and further heat-treated to the T6 temper condition based on the standard ASTM temper designation procedures. Split-Hopkinson pressure bar experiment was used to generate true stress-strain data for the alloy in the range of 1000–3500 /s strain rates while high-speed cameras were used to monitor the test compliance with strain-rate constancy measures. The microstructures of the as received and deformed specimens were assessed and compared for possible disparities in their initial microstructures and post-deformation changes, respectively, using optical microscopy. Results showed no clear evidence of strain-rate dependency in the dynamic yield strength behavior of T6-temper designated alloy while exhibiting a negative trend in its flow stress response. On the contrary, AA2519-T8 showed marginal but positive response in both yield strength and flow behavior for the range of strain rates tested. Post-deformation photomicrographs show clear disparities in the alloys’ initial microstructures in terms of the second-phase particle size differences, population density and, distribution; and in the morphological changes which occurred in the microstructures of the different materials during large plastic deformation. AA2519-T6 showed a higher susceptibility to adiabatic shear localization than AA2519-T8, with deformed and bifurcating transformed band occurring at 3000 /s followed by failure at 3500 /s.

scholarly journals Strain Rate-Dependent Constitutive and Low Stress Triaxiality Fracture Behavior Investigation of 6005 Al Alloy

2018 ◽  
Vol 2018 ◽  
pp. 1-14 ◽  
Author(s):  
Yong Peng ◽  
Xuanzhen Chen ◽  
Shan Peng ◽  
Chao Chen ◽  
Jiahao Li ◽  
...  
Keyword(s):  
Flow Stress ◽  
Plastic Strain ◽  
Strain Rate ◽  
Fracture Behavior ◽  
Equivalent Plastic Strain ◽  
Stress Triaxiality ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Stress States

In order to study the dynamic and fracture behavior of 6005 aluminum alloy at different strain rates and stress states, various tests (tensile tests at different strain rates and tensile shearing tests at five stress states) are conducted by Mechanical Testing and Simulation (MTS) and split-Hopkinson tension bar (SHTB). Numerical simulations based on the finite element method (FEM) are performed with ABAQUS/Standard to obtain the actual stress triaxialities and equivalent plastic strain to fracture. The results of tensile tests for 6005 Al show obvious rate dependence on strain rates. The results obtained from simulations indicate the feature of nonmonotonicity between the strain to fracture and stress triaxiality. The equivalent plastic strain reduces to a minimum value and then increases in the stress triaxiality range from 0.04 to 0.30. A simplified Johnson-Cook (JC) constitutive model is proposed to depict the relationship between the flow stress and strain rate. What is more, the strain-rate factor is modified using a quadratic polynomial regression model, in which it is considered to vary with the strain and strain rates. A fracture criterion is also proposed in a low stress triaxiality range from 0.04 to 0.369. Error analysis for the modified JC model indicates that the model exhibits higher accuracy than the original one in predicting the flow stress at different strain rates. The fractography analysis indicates that the material has a typical ductile fracture mechanism including the shear fracture under pure shear and the dimple fracture under uniaxial tensile.

An Integral Method to Determine Workpiece Flow Stress and Friction Characteristics in Metal Cutting

2015 ◽  
Vol 9 (6) ◽  
pp. 775-781
Author(s):  
Norfariza Wahab ◽  
◽  
Yumi Inatsugu ◽  
Satoshi Kubota ◽  
Soo-Young Kim ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Cutting Forces ◽  
High Speed ◽  
Metal Cutting ◽  
Cutting Edge ◽  
Cutting Process ◽  
Machining Parameters ◽  
Friction Characteristics ◽  
High Speed Cutting

In recent times, numerical simulation techniques have been commonly used to estimate and predict machining parameters such as cutting forces, stresses, and temperature distribution. However, it is very difficult to estimate the flow stress of a workpiece and the friction characteristics at a tool/chip interface, particularly during a high-speed cutting process. The objective of this study is to improve the accuracy of the present method and simultaneously determine the characteristics of the flow stress of a workpiece and friction at the cutting edge under a high strain rate and temperature during the cutting process. In this study, the Johnson-Cook (JC) flow stress model is used as a function of strain, strain rate, and temperature. The friction characteristic was estimated by minimizing the difference between the predicted and measured results of principal force, thrust force, and shear angle. The shear friction equation was used to estimate the friction characteristics. Therefore, by comparing the measured values of the cutting forces with the predicted results from FEM simulations, an expression for workpiece flow stress and friction characteristics at the cutting edge during a high-speed cutting process was estimated.

Investigation on Hardening and Softening Behavior of Steel after Rapid Strain Rate Changes

2016 ◽  
Vol 716 ◽  
pp. 121-128 ◽  
Author(s):  
Jens Dierdorf ◽  
Johannes Lohmar ◽  
Gerhard Hirt
Keyword(s):  
Flow Stress ◽  
Dynamic Recrystallization ◽  
Strain Rate ◽  
Metal Forming ◽  
Elevated Temperatures ◽  
Relaxation Behavior ◽  
Rate Change ◽  
Strain Rates ◽  
Flow Curves ◽  
Strain Rate Change

The design of industrial hot metal forming processes nowadays is mostly carried out using commercial Finite Element (FE) software codes. For precise FE simulations, reliable material properties are a crucial factor. In bulk metal forming, the most important material property is the materials flow stress, which determines the form filling and the necessary forming forces. At elevated temperatures, the flow stress of steels is determined by strain hardening, dynamic recovery and partly by dynamic recrystallization, which is dependent on strain rate and temperature. To simulate hot forming processes, which are often characterized by rapidly changing strain rates and temperatures, the flow stress is typically derived from flow curves, determined at arbitrary constant temperatures and strain rates only via linear interpolation. Hence, the materials instant reaction and relaxation behavior caused by rapid strain rate changes is not captured during simulation. To investigate the relevance of the relaxation behavior for FE simulations, trails with abrupt strain rate change are laid out and the effect on the material flow stress is analyzed in this paper. Additionally, the microstructure evolution due to the strain rate change is investigated. For this purpose, cylinder compression tests of an industrial case hardening steel are conducted at elevated temperatures and different strain rates. To analyze the influence of rapid strain rate changes, changes by one power of ten are performed at a strain of 0.3. As a reference, flow curves of the same material are determined at the initial and final constant strain rate. To investigate the microstructure evolution, compression samples are quenched at different stages, before and after the strain rate change. The results show that the flow curves after the strain rate change tend to approximate the flow curves measured for the final strain rate. However, directly after the strain rate change significant differences between the assumed instant flow stress and the real material behavior can be observed. Furthermore, it can be shown that the state of dynamic recrystallization at the time of the strain rate change influences the material response and relaxation behavior resulting in different slopes of the investigated flow curves after the strain rate change.

Modeling the Hot Deformation Behavior of 1565ch Aluminum Alloy

2016 ◽  
Vol 684 ◽  
pp. 35-41 ◽  
Author(s):  
S.V. Rushchits ◽  
E.V. Aryshensky ◽  
S.M. Sosedkov ◽  
A.M. Akhmed'yanov
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Static Recrystallization ◽  
Strain Rates ◽  
Strain Resistance ◽  
Hot Deformation Behavior ◽  
Zirconium Addition

The deformation behavior of 1565ch alloy under the plane-strain conditions in the temperature range of 350–490 оС and strain rates range of 0,1–10 s-1 is studied. The expression for steady flow stress as the functions of temperature of deformation and strain rate is obtained. It is established that 1565ch alloy with zirconium addition shows higher strain resistance and less tendency to dynamic and static recrystallization than AMg6.

Effect of Directional Grain Structure and Strain Rate on Impact Properties and Dislocation Substructure of 6061-T6 Aluminum Alloy

2014 ◽  
Vol 626 ◽  
pp. 50-56
Author(s):  
Woei Shyan Lee ◽  
Mao Hung Liu
Keyword(s):  
Aluminum Alloy ◽  
Flow Stress ◽  
Strain Rate ◽  
Dislocation Substructure ◽  
Grain Structure ◽  
Strain Rates ◽  
Multiplication Rate ◽  
Impact Properties ◽  
Transverse Specimen ◽  
Longitudinal Specimen

The effect of directional grain structure and strain rate on the impact properties and dislocation substructure of 6061-T6 aluminum alloy is studied. Impact tests are performed at strain rates ranging from 1x103 to 5x103s-1 using a split Hopkinson pressure bar system. Cylindrical specimens are prepared from the rolled plates in longitudinal direction, transverse direction and through-thickness direction, respectively. The results show that the flow stress is strongly dependent on the strain rate and displays complex variations with grain structure direction. The flow stress increases with increasing strain rate. For all tested strain rates, the flow stress is the highest in the transverse specimen, followed by the through-thickness specimen and longitudinal specimen. However, at the strain rate of 5x103s-1, the flow stress in longitudinal specimen is higher than that in through-thickness specimen due to the change of dislocation multiplication rate. The plastic flow occurs within the deformation regions, and becomes more pronounced at high strain rates, especially for the longitudinal specimen. Dislocation density increases markedly with increasing strain rate. Strengthening effect is the highest in the transverse specimen, followed by the longitudinal specimen and through-thickness specimen.

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