scholarly journals Experimental determination and numerical prediction of the dynamic forming limits of a press hardened steel

2021 ◽  
Author(s):  
Nathalie Weiß-Borkowski ◽  
Junhe Lian ◽  
Anne Suse Schulz-Beenken ◽  
Thomas Tröster
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Rate Sensitivity ◽  
Numerical Prediction ◽  
Forming Limit ◽  
Failure Behavior ◽  
Rate Dependency ◽  
Strength Failure ◽  
Force Criterion ◽  
Automotive Steel

Material characteristics such as yield strength, failure strain, strain hardening and strain rate sensitivity parameter are affected by loading speed. Therefore, the strain rate dependency of materials for plasticity and failure behavior is taken into account in crash simulations. Moreover, a possibility for consideration of instability at multi-axial dynamic loadings in crash simulations is the use of dynamic forming limit curves (FLC). In this study, the dynamic FLC of the press hardened automotive steel Usibor 1500 (AlSi coated 22MnB5) is investigated. The experimental results are obtained from a unique high-speed Nakajima setup. Two models are used for the numerical prediction. One is the numerical algorithm CRACH as part of the modular material and failure model MF GenYld+CrachFEM 4.2. Furthermore, the extended modified maximum force criterion considering the strain rate effect is also used to predict the dynamic FLC. The comparison of the experimental and numerical results are presented and discussed.

scholarly journals Characterization of the Formability of High-Purity Polycrystalline Niobium Sheets for SRF Applications

2021 ◽  
pp. 1-19
Author(s):  
Jean-Francois Croteau ◽  
Guillaume Robin ◽  
Elisa Cantergiani ◽  
Said Atieh ◽  
Nicolas Jacques ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
High Purity ◽  
High Speed ◽  
Theoretical Calculations ◽  
Rate Sensitivity ◽  
Forming Limit Diagram ◽  
Forming Limit ◽  
Zone Model ◽  
Nominal Strain Rate

Abstract The forming limit diagram of high-purity niobium sheets used for the manufacturing of superconducting radiofrequency (SRF) cavities is presented. The Marciniak (in-plane) test was used with niobium blanks with a thickness of 1 mm and blank carriers of annealed oxygen-free electronic copper. A high formability was measured, with an approximate true major strain at necking for plane-strain of 0.441. The high formability of high-purity niobium is likely caused by its high strain rate sensitivity of 0.112. Plastic strain anisotropies (r-values) of 1.66, 1.00, and 2.30 were measured in the 0°, 45°, and 90° directions. However, stress–strain curves at a nominal strain rate of ~10−3 s−1 showed similar mechanical properties in the three directions. Theoretical calculations of the forming limit curves (FLCs) were conducted using an analytical two-zone model. The obtained results indicate that the anisotropy and strain rate sensitivity of niobium affect its formability. The model was used to investigate the influence of strain rate on strains at necking. The obtained results suggest that the use of high-speed sheet forming should further increase the formability of niobium.

The Effect of Strain-Rate Upon the Tensile Deformation of Materials

1975 ◽  
Vol 97 (2) ◽  
pp. 151-155 ◽  
Author(s):  
R. G. Davies ◽  
C. L. Magee
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
High Speed ◽  
Tensile Deformation ◽  
Rate Sensitivity ◽  
Al Alloys ◽  
Reinforced Plastics ◽  
Strain Behavior ◽  
Static Testing ◽  
Dynamic Factors

The tensile strength of seventeen engineering materials including steels, Al alloys, and fiber-reinforced plastics, has been determined at strain-rates from 10−3 to 103 sec−1. Variable effects on the stress-strain behavior were found in the different materials with the Al alloys showing minimal strain-rate sensitivity and the plastics highest. All results exhibit a logarithmic dependence of flow stress on strain-rate and thus the dynamic factors (ratio of dynamic to low rate or quasi-static strengths) are as dependent upon changes in quasi-static testing speed (∼1 in./min (0.42 mm/s) as they are to changes at high speed (50,000 in./min or 50 mph (22.35 m/s). No significant influence of strain-rate on elongation or reduction in area has been found for any of the materials. Steels, which comprise the majority of the presently investigated materials, exhibit a higher rate sensitivity for yielding than for higher strain deformation. It is shown that the flow stress results for these steels leads to an internally consistent scheme when (1) strength level and (2) strengthening mechanisms are properly accounted for.

scholarly journals Strain rate and thermal softening effects in shear testing of AA7075-T6 sheet

2018 ◽  
Vol 183 ◽  
pp. 02037 ◽  
Author(s):  
Taamjeed Rahmaan ◽  
Ping Zhou ◽  
Cliff Butcher ◽  
Michael J. Worswick
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Rate Sensitivity ◽  
Thermal Conditions ◽  
Shear Loading ◽  
Image Correlation ◽  
High Rate ◽  
Strain Rates ◽  
Shear Testing ◽  
Plane Shear

Shear tests were performed at strain rates ranging from quasi-static (0.01 s-1) to 500 s-1 for AA7075-T6 sheet metal alloy at room temperature. A miniature sized shear specimen was used in this work to perform high strain rate shear testing. Digital image correlation (DIC) techniques were employed to measure the strains in the experiments. At maximum in-plane shear strains greater than 20%, the AA7075-T6 alloy demonstrated a reduced work hardening rate at elevated strain rates. At lower strains, the AA7075-T6 alloy showed mild positive rate sensitivity. The strain to localization (using the Zener-Holloman criterion), measured using the DIC technique, decreased with strain rate in shear loading. The strain at complete failure, however, exhibited an increase at the highest strain rate (500 s-1). The current work also focused on characterization of the thermal conditions occurring during high rate loading in shear with in situ high speed thermal imaging. Experimental results from the highest strain rate (500 s-1) tests showed a notable increase in temperature within the specimen gauge region as a result of the conversion of plastic deformation energy into heat.

scholarly journals Tensile and Stress-Rupture Behavior of Hafnium Carbide Dispersed Molybdenum and Tungsten Base Alloy Wires

1993 ◽  
Vol 322 ◽  
Author(s):  
H.M. Yun ◽  
R.H. Titran
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rupture Strength ◽  
Base Alloy ◽  
Stress Rupture ◽  
Rate Sensitivity ◽  
Tungsten Alloy ◽  
Rate Dependency ◽  
Hafnium Carbide ◽  
Stress Rupture Strength

AbstractThe tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 µm in diameter, were determined over the temperature range from 1200 to 1600 K. Three molybdenum alloy wires; Mo + 1.1 wt% hafnium carbide (MoHfC), Mo + 25 wt% W + 1.1 wt% hafnium carbide (MoHfC+25W) and Mo + 45 wt% W + 1.1 wt% hafnium carbide (MoHfC+45W), and a W + 0.4 wt% hafnium carbide (WHfC) tungsten alloy wire were evaluated.The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress-rupture strength at temperatures above 1400 K.

Quasi-Static and Dynamic Compressive Properties of AZ31 Magnesium Alloy Processed by Equal Channel Angular Pressing

2014 ◽  
Vol 566 ◽  
pp. 86-91
Author(s):  
Xia Yu ◽  
Tao Suo ◽  
Feng Zhao ◽  
Yu Long Li
Keyword(s):  
Magnesium Alloy ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Rate Sensitivity ◽  
Compressive Properties ◽  
Compression Properties ◽  
Angular Pressing ◽  
Strength Failure ◽  
Dynamic Loadings ◽  
Az31b Alloy

Equal channel angular pressing (ECAP) was applied to control the microstructure of AZ31B magnesium alloy. Compression properties of both as-received and grain refined AZ31B alloy were investigated under quasi-static and dynamic loadings. The yield strength, ultimate strength, failure strain and flow stress under compression loading were studied. Both the as-received alloy and ECAPed alloy show strong strain rate sensitivity. Grain size, texture and strain rate jointly affect the deformation mechanisms. Through fractography analysis, the fracture mechanism was analyzed.

FAILURE BEHAVIORS OF FLIP CHIP SOLDER JOINTS UNDER VARIOUS LOADING CONDITIONS OF HIGH-SPEED SHEAR TEST

2009 ◽  
Vol 23 (06n07) ◽  
pp. 1809-1815 ◽  
Author(s):  
SANG-SU HA ◽  
SANG-OK HA ◽  
JIN-KYU JANG ◽  
JONG-WOONG KIM ◽  
JONG-BUM LEE ◽  
...  
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Shear Test ◽  
Flip Chip ◽  
Solder Joints ◽  
Rate Sensitivity ◽  
Loading Conditions ◽  
3 Dimensional ◽  
Dimensional Finite Element ◽  
Shear Speed

The failure behaviors of flip chip solder joints under various loading conditions of the high-speed shear test (H-SST) were investigated with an experimental and non-linear 3-dimensional finite element modeling study. The solder composition used in this study was Sn -3.0 Ag -0.5 Cu ( in wt .%). The shear forces were far greater by H-SST than by low-speed shear test (L-SST). The shear force further increased with increasing shear speed, mainly due to the high strain-rate sensitivity of the solder alloy. Brittle interfacial fractures were more easily achieved by H-SST, especially at the higher shear speed. This was discussed in terms of the relationship between the strain-rate and work-hardening effect and the resulting stress concentration at the interfacial regions

Mechanical Anisotropy and Strain Rate Dependency Behavior of Ti6Al4V Produced Using E-Beam Additive Fabrication

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Leila Ladani ◽  
Jafar Razmi ◽  
Soud Farhan Choudhury
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Mechanical Anisotropy ◽  
Rate Dependency ◽  
Out Of Plane ◽  
Degree Of Anisotropy ◽  
Strain Rate Dependency

Anisotropic mechanical behavior is an inherent characteristic of parts produced using additive manufacturing (AM) techniques in which parts are built layer by layer. It is expected that in-plane and out-of-plane properties be different in these parts. E-beam fabrication is not an exception to this. It is, however, desirable to keep this degree of anisotropy to a minimum level and be able to produce parts with comparable mechanical strength in both in-plane and out-of-plane directions. In this manuscript, this degree of anisotropy is investigated for Ti6Al4V parts produced using this technique through tensile testing of parts built in different orientations. Mechanical characteristics such as Young's modulus, yield strength (YS), ultimate tensile strength (UTS), and ductility are evaluated. The strain rate effect on mechanical behavior, namely, strength and ductility, is also investigated by testing the material at a range of strain rates from 10−2 to 10−4 s−1. Local mechanical properties were extracted using nanoindentation technique and compared against global values (average values obtained by tensile tests). Although the properties obtained in this experiment were comparable with literature findings, test results showed that in-plane properties, elastic modulus, YS, and UTS are significantly higher than out-of-plane properties. This could be an indication of defects in between layers or imperfect bonding of the layers. Strong positive strain rate sensitivity was observed in out-of-plane direction. The strain rate sensitivity evaluation did not show strain rate dependency for in-plane directions. Local mechanical properties obtained through nanoindentation confirmed the findings of tensile test and also showed variation of properties caused by geometry.

Peeling Rate Dependency of Delamination Behavior of Adhesives

2008 ◽  
Vol 33-37 ◽  
pp. 339-344 ◽  
Author(s):  
Ryota Masuda ◽  
Hirotsugu Inoue ◽  
Kikuo Kishimoto
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Cohesive Zone Model ◽  
Base Material ◽  
Interfacial Strength ◽  
Video Camera ◽  
Zone Model ◽  
Rate Dependency ◽  
Element Analysis ◽  
Rate Region

Adhesives are widely used in our life and industrial world. However, it is difficult to characterize their mechanical properties because those strongly depend on environmental and mechanical conditions such as temperature, humidity or strain rate. In this paper, we focus on the strain rate dependence of the interfacial strength and investigate the interfacial strength by peel tests under several peel rates. The results show that, in lower rate region (under 1.0 mm/s), the interfacial strength is constant and, in transition region (1.0 to 10 mm/s) the interface strength increased with the peel rate. In middle rate region (10 to 103 mm/s), the interfacial strength is constant again. Over 103 mm/s region, the interfacial strength drops and became lower than those in middle rate cases. From the observation of peeling front by a high speed video camera, the deformation behavior of adhesives changes with the peel rate.􀀁Finite element analysis by using cohesive zone model is also conducted, and influence of the rate dependency of adhesive and base material is discussed.

Rubber Structural Coupon Behaviour Study under Pressure Impulse

2013 ◽  
Vol 198 ◽  
pp. 394-399
Author(s):  
Pawel Baranowski ◽  
Jerzy Malachowski ◽  
Łukasz Mazurkiewicz ◽  
Krzysztof Damaziak
Keyword(s):  
Strain Rate ◽  
Time Integration ◽  
Rate Sensitivity ◽  
Rate Dependency ◽  
Material Behaviour ◽  
Explicit Integration ◽  
Dynamic Simulations ◽  
Central Difference ◽  
Strain Rate Effects ◽  
Behaviour Study

This study focuses on the rubber material behaviour assessment under dynamic loading using numerical methods. Consequently, dynamic simulations of the rubber structural coupon subjected to dynamic velocity loading were performed using the explicit integration procedure with central difference scheme with modified time integration of the equation of motion implementation. During investigations two impulse velocities were used and compared for two different constitutive materials: Mooney-Rivlin without rate-dependency and Mat 181 Simplified Rubber which includes strain rate effects. From the obtained results it was noticed that material behaviour in both cases is different and along with different values of velocity the strain rate sensitivity changes.

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