Behaviors of three BCC metal over a wide range of strain rates and temperatures: experiments and modeling

In this paper the first results of the mechanical characterization in tension of two high strength alloys in a wide range of strain rates are presented. Different experimental techniques were used for different strain rates: a universal machine, a Hydro-Pneumatic Machine and a JRC-Split Hopkinson Tensile Bar. The experimental research was developed in the DynaMat laboratory of the University of Applied Sciences of Southern Switzerland. An increase of the stress at a given strain increasing the strain-rate from 10-3 to 103 s-1, a moderate strain-rate sensitivity of the uniform and fracture strain, a poor reduction of the cross-sectional area at fracture with increasing the strain-rate were shown. Based on these experimental results the parameters required by the Johnson-Cook constitutive law were determined.

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Deformation behavior of 42CrMo4 over a wide range of temperatures and strain rates in Split-Hopkinson pressure bar tests

Materials Science and Engineering A ◽

10.1016/j.msea.2021.141953 ◽

2021 ◽

pp. 141953

Author(s):

Janis S. Kimm ◽

Jim A. Bergmann ◽

Florian Wöste ◽

Fabian Pöhl ◽

Petra Wiederkehr ◽

...

Keyword(s):

Deformation Behavior ◽

Split Hopkinson Pressure Bar ◽

Strain Rates ◽

Hopkinson Pressure Bar ◽

Wide Range ◽

Split Hopkinson ◽

Pressure Bar

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INVESTIGATING THE INFLUENCE OF ENVIRONMENTAL CONDITIONING ON EPOXY RESINS AT QUASISTATIC AND HIGH STRAIN RATES FOR MATERIAL OPERATING LIMIT

10.12783/asc36/35745 ◽

2021 ◽

Author(s):

SAGAR M. DOSHI, SAGAR M. DOSHI, ◽

NITHINKUMAR MANOHARAN ◽

BAZLE Z. (GAMA) HAQUE, ◽

JOSEPH DEITZEL ◽

JOHN W. GILLESPIE, JR.

Keyword(s):

Mechanical Properties ◽

Epoxy Resin ◽

Yield Stress ◽

High Strain ◽

Operating Conditions ◽

Strain Rates ◽

High Strain Rates ◽

Stress Strain ◽

Wide Range ◽

Environmental Aging

Epoxy resin-based composite panels used for armors may be subjected to a wide range of operating temperatures (-55°C to 76°C) and high strain rates on the order of 103-104 s-1. Over the life cycle, various environmental factors also affect the resin properties and hence influence the performance of the composites. Therefore, it is critical to determine the stress-strain behavior of the epoxy resin over a wide range of strain rates and temperatures for accurate multi-scale modeling of composites and to investigate the influence of environmental aging on the resin properties. Additionally, the characterization of key mechanical properties such as yield stress, modulus, and energy absorption (i.e. area under the stress-strain curve) at varying temperatures and moisture can provide critical data to calculate the material operating limits. In this study, we characterize mechanical properties of neat epoxy resin, SC-15 (currently used in structural armor) and RDL-RDC using uniaxial compression testing. RDL-RDC, developed by Huntsman Corporation, has a glass transition temperature of ~ 120°C, compared to ~ 85°C of SC-15. A split Hopkinson pressure bar is used for high strain rate testing. Quasistatic testing is conducted using a screw-driven testing machine (Instron 4484) at 10-3 s-1 and 10-1 s-1 strain rates and varying temperatures. The yield stress is fit to a modified Eyring model over the varying strain rates at room temperature. For rapid investigation of resistance to environmental aging, accelerated aging tests are conducted by immersing the specimens in 100°C water for 48 hours. Specimens are conditioned in an environmental chamber at 76 °C and 88% RH until they reach equilibrium. Tests are then conducted at five different temperatures from 0°C to 95°C, and key mechanical properties are then plotted vs. temperature. The results presented are an important step towards developing a methodology to identify environmental operating conditions for composite ground vehicle applications.

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Mechanical behavior of DP780 dual phase steel at a wide range of strain rates

Materials Research Express ◽

10.1088/2053-1591/aad7ea ◽

2018 ◽

Vol 5 (9) ◽

pp. 096519 ◽

Cited By ~ 2

Author(s):

Shengci Li ◽

Lan Zhang ◽

Hongjin Zhao ◽

Liang Qi ◽

Yonglin Kang

Keyword(s):

Mechanical Behavior ◽

Dual Phase Steel ◽

Dual Phase ◽

Strain Rates ◽

Wide Range

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Rheo-Optics Studies in the Development of Hybrid Liquid Crystalline Based Mwir Polarizers

MRS Proceedings ◽

10.1557/proc-559-51 ◽

1999 ◽

Vol 559 ◽

Author(s):

P.T. Mather ◽

W. Barnes ◽

P.J. Hood ◽

T.J. Bunning

Keyword(s):

Liquid Crystalline ◽

Flow Behavior ◽

Optical Microscope ◽

Processing Technique ◽

Strain Rates ◽

Alignment Layer ◽

Small Pitch ◽

Wide Range ◽

Measured Polarization ◽

Free Films

ABSTRACTWe present here a rheo-optical study of the flow behavior of two cholesteric liquid crystals, one with a large pitch and one with a small pitch. The large pitch compound has been investigated as a possible fixed wavelength polarizer in the mid-wavelength infra-red region (3-5 micron). The investigation of these compounds is driven by their low melt viscosity and ability to vitrify order, and thus functionality, into films with a wide range of thickness. In our attempts to obtain consistent thin films with reproducible contrast ratios, we explored the defect textures of both compounds under a polarizing optical microscope. These materials were sheared at various strain rates and at various temperatures in an attempt to determine the best processing window for defect free films. The pitch lengths of the two materials investigated were 160 and 1330 nm. The flow behavior of the large pitch material resembles a pure nematic with defect refinement taking place under flow. The short pitch material exhibited the typical Grandjean oily streaks upon shearing followed by coarsening. Observations made during this rheological study were used to identify a processing technique for the large pitch materials. Upon application of a conventional buffed alignment layer, films with consistent quality were routinely made. The measured polarization contrast of >70:1 exceeds the values obtained from state-of-the art commercial polarizers in this wavelength regime.

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