Empirical Equations for a Study on Strain Rate Sensitivity of Polypropylene Syntactic Foam

2010 ◽  
Vol 143-144 ◽  
pp. 303-307
Author(s):  
En Yang Wang ◽  
Masaki Omiya
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Viscoelastic Properties ◽  
Elastic Moduli ◽  
Syntactic Foam ◽  
Rate Sensitivity ◽  
Empirical Equations ◽  
Syntactic Foams ◽  
Nominal Strain Rate ◽  
Nominal Strain

The strain rate sensitivity of polypropylene syntactic foams with polymer microballoons in the relative density from 0.5 to 0.8 is studied at the nominal strain rate ranged from 10-1 to 102 s -1. Two equations of matrix materials are introduced to represent the viscoelastic properties, and another two equations are proposed with respect to the parameters of matrix materials to estimate the elastic moduli and yield stresses of polymeric syntactic foams.

scholarly journals High Strain Rate Compressive Behavior of Polyurethane Resin and Polyurethane/Al2O3 Hollow Sphere Syntactic Foams

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Dung D. Luong ◽  
Vasanth Chakravarthy Shunmugasamy ◽  
Oliver M. Strbik III ◽  
Nikhil Gupta
Keyword(s):  
Compressive Strength ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
High Strain ◽  
Syntactic Foam ◽  
Rate Sensitivity ◽  
Syntactic Foams ◽  
Polyurethane Resin ◽  
Important Concern ◽  
Quasistatic Regime

Polyurethane resins and foams are finding extensive applications. Seat cushions and covers in automobiles are examples of these materials. In the present work, hollow alumina particles are used as fillers in polyurethane resin to develop closed-cell syntactic foams. The fabricated syntactic foams are tested for compressive properties at quasistatic and high strain rates. Strain rate sensitivity is an important concern for automotive applications due to the possibility of crash at high speeds. Both the polyurethane resin and the syntactic foam show strain rate sensitivity in compressive strength. It is observed that the compressive strength increases with strain rate. The energy absorbed up to 10% strain in the quasistatic regime is 400% higher for the syntactic foam in comparison to that of neat resin at the same strain rate.

A Microscopic Study on Local Strain Rate Sensitivity of Polypropylene Syntactic Foam with Microballoons

2010 ◽  
Vol 160-162 ◽  
pp. 1280-1284
Author(s):  
En Yang Wang ◽  
Masaki Omiya
Keyword(s):  
Strain Rate ◽  
Microscopic Study ◽  
Strain Rate Sensitivity ◽  
Syntactic Foam ◽  
Rate Sensitivity ◽  
Local Strain ◽  
Local Strain Rate

A Microscopic Study on Local Strain Rate Sensitivity of Polypropylene Syntactic Foam with Microballoons

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.

scholarly journals Negative Strain Rate Sensitivity Induced by Structure Heterogeneity in Zr64.13Cu15.75Ni10.12Al10 Bulk Metallic Glass

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 339
Author(s):  
Xiang Wang ◽  
Zhi Qiang Ren ◽  
Wei Xiong ◽  
Si Nan Liu ◽  
Ying Liu ◽  
...  
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Strain Rate Sensitivity ◽  
Critical Role ◽  
Rate Sensitivity ◽  
Confined Compression ◽  
Negative Strain Rate Sensitivity ◽  
Cast Specimen ◽  
Structure Heterogeneity

The negative strain rate sensitivity (SRS) of metallic glasses is frequently observed. However, the physical essence involved is still not well understood. In the present work, small-angle X-ray scattering (SAXS) and high-resolution transmission electron microscopy (HRTEM) reveal the strong structure heterogeneity at nanometer and tens of nanometer scales, respectively, in bulk metallic glass (BMG) Zr64.13Cu15.75Ni10.12Al10 subjected to fully confined compression processing. A transition of SRS of stress, from 0.012 in the as-cast specimen to −0.005 in compression processed specimen, was observed through nanoindentation. A qualitative formulation clarifies the critical role of internal stress induced by structural heterogeneity in this transition. It reveals the physical origin of this negative SRS frequently reported in structurally heterogeneous BMG alloys and its composites.

Strain rate sensitivity of a 1.5 GPa nanotwinned steel

2021 ◽  
Author(s):  
R.D. Liu ◽  
Y.Z. Li ◽  
L. Lin ◽  
C.P. Huang ◽  
Z.H. Cao ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity

scholarly journals The Strain Rate Sensitivity and Creep Behavior for the Tripler Plane of Potassium Dihydrogen Phosphate Crystal by Nanoindentation

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 369
Author(s):  
Jianhui Mao ◽  
Wenjun Liu ◽  
Dongfang Li ◽  
Chenkai Zhang ◽  
Yi Ma
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Creep Deformation ◽  
Potassium Dihydrogen Phosphate ◽  
Rate Sensitivity ◽  
Dislocation Nucleation ◽  
Machining Process ◽  
Dihydrogen Phosphate ◽  
Potassium Dihydrogen ◽  
Kdp Crystals

As an excellent multifunctional single crystal, potassium dihydrogen phosphate (KDP) is a well-known, difficult-to-process material for its soft-brittle and deliquescent nature. The surface mechanical properties are critical to the machining process; however, the characteristics of deformation behavior for KDP crystals have not been well studied. In this work, the strain rate effect on hardness was investigated on the mechanically polished tripler plane of a KDP crystal relying on nanoindentation technology. By increasing the strain rate from 0.001 to 0.1 s−1, hardness increased from 1.67 to 2.07 GPa. Hence, the strain rate sensitivity was determined as 0.053, and the activation volume of dislocation nucleation was 169 Å3. Based on the constant load-holding method, creep deformation was studied at various holding depths at room temperature. Under the spherical tip, creep deformation could be greatly enhanced with increasing holding depth, which was mainly due to the enlarged holding strain. Under the self-similar Berkovich indenter, creep strain could be reduced at a deeper location. Such an indentation size effect on creep deformation was firstly reported for KDP crystals. The strain rate sensitivity of the steady-state creep flow was estimated, and the creep mechanism was qualitatively discussed.

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