scholarly journals Effects of Temperature and Strain Rate on the Fracture Behaviors of an Al-Zn-Mg-Cu Alloy

Materials ◽  
2018 ◽  
Vol 11 (7) ◽  
pp. 1233 ◽  
Author(s):  
Yue Guo ◽  
Mingxing Zhou ◽  
Xingdong Sun ◽  
Long Qian ◽  
Lijia Li ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Peak Stress ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Cu Alloy ◽  
Deformation State ◽  
Wide Range ◽  
Fracture Behaviors ◽  
Effects Of Temperature

Effects of temperature and strain rate on the fracture behaviors of an Al-Zn-Mg-Cu alloy are investigated by isothermal uniaxial tensile experiments at a wide range of temperatures and strain rates, from room temperature (RT) to 400 °C and from 10−4 s−1 to 10−1 s–1, respectively. Generally, the elevation of temperature leads to the increasing of elongation to fracture and the reduction of peak stress, while higher strain rate results in the decreasing of elongation to fracture and the increasing of peak stress. Interestingly, we found that the coefficient of strain rate sensitivity (m-value) considerably rises at 200 °C and work of fracture (Wf) fluctuates drastically with the increase of strain rate at RT and 100 °C, both of which signify a non-uniform and unstable deformation state below 200 °C. A competition of work hardening (WH) and dynamic recrystallization (DRX) exists at 200 °C, making it serve as a transitional temperature. Below 200 °C, WH is the main deformation mechanism of flow stress, and DRX dominates the flow stress above 200 °C. It has been found that from RT to 200 °C, the main feature of microstructure is the generation of dimples and microvoids. Above 200 °C, the coalescence of dimples and microvoids mainly leads to the failure of specimen, while the phenomenon of typically equiaxed dimples and nucleation appear at 400 °C. The observations of microstructure are perfectly consistent with the related macroscopic results. The present work is able to provide a comprehensive understanding of flow stress of an Al-Zn-Mg-Cu alloy at a wide range of temperatures and strain rates, which will offer valuable information to the optimization of the hot forming process and structural design of the studied alloy.

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.

Behavior of Flow Stress of Al-Mn Alloy during Hot Compression

2014 ◽  
Vol 886 ◽  
pp. 109-114
Author(s):  
Xiao Zhang ◽  
Zheng Ren ◽  
Xiu Rong Zhu ◽  
Jing Ren ◽  
Fu Kui Lian ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Peak Stress ◽  
True Stress ◽  
Hot Compression ◽  
Strain Rates ◽  
Steady State Flow ◽  
Temperature Range ◽  
Relationship Of ◽  
The Relationship

The behavior of flow stress of Al-Mn alloy during hot compression at the condition of ε=0.05,0.5,5,25s-1 while the temperature range from 300°C to 450°C was studied by Gleblee-3500. The results show that the Al-Mn alloy possess the remarkable characteristic of a peak stress, followed by a steady-state flow stress when deformed in the temperature range from 300°C to 450°C with a strain rates range from 0.05s-1 to 0.5s-1.When the strain rate is higher than 5s-1 dynamic recrystallization will happen. The true stress decrease with increasing compression temperature and increases with the increasing strain rate. A constitution equation which can describe the relationship of ε,T and σ is achieved. Also the activation energy for deformation is calculated.

Superplastic Forming Properties of TIMETAL®54M (Ti-5%Al-4%V-0.6%Mo-0.4%Fe) Sheets

2010 ◽  
Vol 433 ◽  
pp. 311-317 ◽  
Author(s):  
Yoji Kosaka ◽  
Phani Gudipati
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Total Elongation ◽  
Grain Boundary Sliding ◽  
Strain Rates ◽  
Wide Range ◽  
Boundary Sliding ◽  
Annealed Sheet

Superplastic forming (SPF) properties of TIMETAL54M (Ti-5Al-4V-0.6Mo-0.4Fe, or Ti-54M) sheet were investigated. A total elongation of Ti-54M exceeds 500% at temperatures between 750°C and 850°C at a strain rate of 10-3/S. Values of strain rate sensitivity (m-value) measured by jump strain rate tests are 0.45 ~0.6 in a temperature range of 730°C to 900°C at a strain arte of 5 x 10-4/S or 1 x 10-4/S. Flow stress of the alloy is 20 ~ 40% lower than that of Ti-6Al-4V (Ti-64) mill annealed sheet. The observation of microstructure after the tests revealed the indication of grain boundary sliding in a wide range of temperatures and strain rates.

scholarly journals SENSITIVITY OF THE FLOW STRESS OF NYLON 6 AND NYLON 66 TO STRAIN-RATE

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1249-1254 ◽  
Author(s):  
ISSAM BENACEUR ◽  
RAMZI OTHMAN ◽  
PIERRICK GUEGAN ◽  
ABDERRAZEK DHIEB ◽  
FAKHREDDINE DAMEK
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Polymer Matrix Composites ◽  
Nylon 6 ◽  
Strain Rates ◽  
Matrix Composites ◽  
Nylon 66 ◽  
Mechanics Of Materials ◽  
Study Results ◽  
Wide Range

The sensitivity of the flow stress of polymers to strain-rate is one of the major concerns in mechanics of materials since polymers and polymer matrix composites are widely used in many engineering applications. In this paper, we present tests on Nylon 6 and Nylon 66 on wide range of strain-rates (0.001-5000 s −1). Specifically, we used INSTRON machine for low strain-rates. The high strain-rate measurements were inferred from the Hopkinson bar tests. Only the compressive behaviour was investigated. To eliminate any interference with temperature and humidity effects, test samples were conditioned at 20°C and 50% of hygrometry. Moreover, the effects of the specimen geometry were considered. The current study results are also compared to values found in literature.

scholarly journals Quasi-Static Loading Responses and Constitutive Modeling of Al–Si–Mg alloy

Metals ◽  
2018 ◽  
Vol 8 (10) ◽  
pp. 838 ◽  
Author(s):  
Zhenglong Liang ◽  
Qi Zhang
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Flow Behavior ◽  
Peak Stress ◽  
Mg Alloy ◽  
Average Error ◽  
Flow Curves ◽  
Modified Model ◽  
Wide Range ◽  
Measured Flow

The flow behavior of the Al–Si–Mg alloy under uniaxial compression loading was investigated at different strain rates (10−3 s−1, 10−2 s−1,10−1 s−1, 100 s−1) at a wide range of temperatures (573 K, 623 K, 673 K, 723 K, 773 K). The results showed that the peak stress increase with the strain rate and decrease with the increase of temperature. According to the measured flow stress curves, a modified Johnson-Cook (J-C) constitutive model taking strain rate effect on thermo softening into account was proposed to delineate the flow behavior. The comparisons between the measured flow curves and the predicted ones showed them to be very close and the average error is 1.65%. The added experiments were also conducted for validating the modified model, and the predicted data well agreed with the measured flow stress curves. That indicated the modified Johnson-Cook model is reliable and can accurately delineate the flow behavior of Al–Si–Mg alloy.

High Strain-Rate Constitutive Behavior of SAC305 Solder During Operation at High Temperature

2014 ◽  
Author(s):  
Pradeep Lall ◽  
Di Zhang ◽  
Vikas Yadav
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
Tensile Tests ◽  
Image Correlation ◽  
Dynamic Strain ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
High Strain Rates ◽  
Wide Range ◽  
Thermal Chamber

Leadfree solders have been used as interconnects in electronic packaging, due to its environmental friendly chemical property. However, those materials may experience high strain rates when subjected to shock and vibration. Consequently, failure will occur to electronics in those situations. Therefore, knowing the material properties of lead-free solders are extremely important, but research on mechanical behaviors of those solder alloys at high strain rates are scarce. Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. However, Anand’s model constants for the transient dynamic strain rates are scarce. In this paper, the nine material parameters to fit the Anand viscoplastic model at high strain rates have been presented. In order to develop the constants for this model, uniaxial tensile tests at several strain rates and temperatures have been completed. A constant strain rate impact hammer which enables attaining strain rates around 1 to 100 per sec has been employed to implement tensile tests and a small thermal chamber is applied to control testing temperature. High speed cameras operating at 70,000 fps have been used to capture images of specimen and then digital image correlation method is used to calculate tensile strain. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε̇ = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125°C). Anand viscoplasticity constants have been calculated by nonlinear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

scholarly journals Strain-Rate and Grain‒Size Effects in Ice

1987 ◽  
Vol 33 (115) ◽  
pp. 274-280 ◽  
Author(s):  
David M. Cole
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Transition Point ◽  
Boundary Migration ◽  
Peak Stress ◽  
Strain Rates ◽  
Thin Sections ◽  
Fine Grained ◽  
Lower Strain ◽  
Polycrystalline Ice

AbstractThis paper presents and discusses the results of constant deformation-rate tests on laboratory-prepared polycrystalline ice. Strain-rates ranged from 10−7to 10−1s−1, grain–size ranged from 1.5 to 5.8 mm, and the test temperature was −5°C.At strain-rates between 10−7and 10−3s−1, the stress-strain-rate relationship followed a power law with an exponent ofn= 4.3 calculated without regard to grain-size. However, a reversal in the grain-size effect was observed: below a transition point near 4 × 10−6s−1the peak stress increased with increasing grain-size, while above the transition point the peak stress decreased with increasing grain-size. This latter trend persisted to the highest strain-rates observed. At strain-rates above 10−3s−1the peak stress became independent of strain-rate.The unusual trends exhibited at the lower strain-rates are attributed to the influence of the grain-size on the balance of the operative deformation mechanisms. Dynamic recrystallization appears to intervene in the case of the finer-grained material and serves to lower the peak stress. At comparable strain-rates, however, the large-grained material still experiences internal micro-fracturing, and thin sections reveal extensive deformation in the grain-boundary regions that is quite unlike the appearance of the strain-induced boundary migration characteristic of the fine-grained material.

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