The WIDL sample for uniaxial tension is well designed to produce a simple single uniaxial tensile mode of deformation and is held so that not to need any extensometry.
The WIDL sample for uniaxial compression is well designed to produce a simple single uniaxial compressive mode of deformation and avoid bulging at the free surfaces.
The WIDL sample for planar tension is designed to ensure planar tension deformation. It minimizes slippage and prevents distortion, delivering reliable results.
The WIDL sample for volumetric compression is well designed to get confined in a cavity to then produce a simple single volumetric compressive mode of deformation.
The WIDL fixture for uniaxial tension testing is designed to produce a simple single uniaxial tensile deformation mode and operates without a need for extensometry.
The WIDL fixture for uniaxial compression is well designed to produce a simple single uniaxial compressive mode of deformation and avoid bulging at the free surfaces.
The WIDL fixture for planar tension is well designed to produce a simple single planar tensile mode of deformation and avoid slippage and reduce hourglass effects.
The WIDL fixture for volumetric compression is well designed to confine a sample in a cavity to then produce a simple single volumetric compressive mode of deformation.
WIDL’s hyper-elastic tester I allows to prepare samples for all deformation modes, condition or age them, then test them, and post-process the data into material models.
WIDL’s hyper-elastic tester II allows to test polymers under independent deformation modes with added test conditions (aeration, fluid circulation, lower temperatures).
WIDL’s leak tester I allows to establish polymer minimum pressure to seal under specified pressures and force-deflections against various finish mating surfaces.
WIDL’s visco-elastic tester I allows to monitor polymer degradation with time and heat, and post-processcollected data into Prony series and WLF shift functions.
The only mode of deformation of hyper-elastic materials like flexible polymers documented in world standards is the uniaxial. Still, standard uniaxial tension “dog-bones” hourglass and standard compression buttons bulge.
Polymer testing is more involved per nonlinearities in material, contacts, and large deformations. Proper testing requires specially designed samples and fixtures, and well-orchestrated tests and data post-processing schemes.
Polymers require test data under uniaxial tension, uniaxial compression, planar tension, and volumetric compression. The data is then used to fit energy density functions (based on strain invariants or stretch ratios) for nonlinear FEA.
Often, simply ignored in product development, design parameters need definition to gauge results of numerical modeling. Some examples? A minimum pressure to seal, a bearable assembly force, a maximum stress to break, etc.
Lightly compressing a seal may lead to leakage and over compressing it may result in breakage and accelerates degradation: Establishing the onset of sealing requires special testing on ring seals besides data analyses.
Polymer degrade with time and temperature, a phenomenon known as visco-elasticity. Monitoring polymer decay requires special samples, machinery, protocols, and test result post-processing into series and shift functions.
Reducing polymer physical testing schedules relies on time-temperature superposition (TTS) in which temperature is scaled and data is plotted in logarithmic scales to establish shift functions complementing Prony series.
Procedures and machinery for material testing this far have followed guidelines of world standards like ASTM, DIN, CSA, etc. With the advent of numerical modeling products, before making any commitments to producing them, testing is shifting to determining parameters like constants and functions in constitutive equations. Such equations are constructed to represent material behaviors for arbitrary strain and loading histories. In the case of nonlinear materials such as polymers, procedures and machinery become necessary to perform experiments on laboratory specimens designed to deform in well-defined strain fields.
“Polymers (rubbers, plastics, foams, etc.) as a category of hyper-elastic materials deform under four basic modes. Their properties also vary with time and temperature, so they are visco-elastic. Many practitioners and companies have developed accessories to test polymers for hyper- and visco-elasticity, but these remain large, costly, non-unified, to say the least. WIDL has tuned, for the past many years, apparatuses and methods for material sample preparations and property generations and analyses, convenient, small scale, complete, it intends now to put on the
market to fill a gap in our industry.”
Reverse-engineering, compound development, fluid compatibility and ageing, characteristics for FEA and CFD modeling, etc.
Mechanical, thermal, time-dependent, frequency-domain, acceleration, TTS, creep, stress-relaxation, etc.
Conceptualization, design, reverse-engineering, CAD, CAE, CAM, FEA, CFD, optimization, sensitivity, LMC/MMC, etc.
Client representations, neutral evaluations, brainstorming, government programs, academia, IP, patents. etc.
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Disclaimer - Dr. Chouchaoui and WIDL do not do engineering services regulated by PEO (Professional Engineers Ontario). If you need services as such please contact PEO for referrals to an engineer who does such.
