Podcast
Questions and Answers
What are the two basic components used in viscoelastic mechanical models?
What are the two basic components used in viscoelastic mechanical models?
- A lever and a dashpot
- A spring and a dashpot (correct)
- A spring and a damper
- A spring and a fluid
In the Maxwell model, how are the spring and dashpot arranged?
In the Maxwell model, how are the spring and dashpot arranged?
- At right angles
- In parallel
- In series (correct)
- In sequence
Which laws are combined to form the explanation of the Maxwell model's behavior?
Which laws are combined to form the explanation of the Maxwell model's behavior?
- Hooke’s law and Newton’s law (correct)
- Faraday's law and Newton’s law
- Ohm's law and Hooke’s law
- Newton's law and Einstein's theory
What does the overall strain in the Maxwell model consist of?
What does the overall strain in the Maxwell model consist of?
Under the action of stress in the Maxwell model, what is true about the stress experienced by the spring and dashpot?
Under the action of stress in the Maxwell model, what is true about the stress experienced by the spring and dashpot?
What is the relationship between strain and time in the Maxwell model?
What is the relationship between strain and time in the Maxwell model?
What does the term 'creep curve' refer to in the context of viscoelastic materials?
What does the term 'creep curve' refer to in the context of viscoelastic materials?
What challenge is often faced when predicting stress relaxation behavior in real polymers?
What challenge is often faced when predicting stress relaxation behavior in real polymers?
What is the relationship between strain (e) and stress (σ) in the context of Voigt model during creep?
What is the relationship between strain (e) and stress (σ) in the context of Voigt model during creep?
Which of the following equations represents creep behavior in the Voigt model?
Which of the following equations represents creep behavior in the Voigt model?
What occurs in the Voigt model when the strain (e) is held constant?
What occurs in the Voigt model when the strain (e) is held constant?
The Voigt model primarily describes which behavior of polymers?
The Voigt model primarily describes which behavior of polymers?
How does the Maxwell model compare to the Voigt model in stress relaxation behavior?
How does the Maxwell model compare to the Voigt model in stress relaxation behavior?
What is represented by the constant ratio η/E in the Voigt model?
What is represented by the constant ratio η/E in the Voigt model?
In which scenario does the strain rate (de/dt) equal zero in the Voigt model?
In which scenario does the strain rate (de/dt) equal zero in the Voigt model?
What is the primary limitation of the Maxwell model in predicting polymer behavior during creep?
What is the primary limitation of the Maxwell model in predicting polymer behavior during creep?
What does the equation $\sigma = \sigma_0 \exp(-\frac{E t}{\eta})$ predict about stress in polymers?
What does the equation $\sigma = \sigma_0 \exp(-\frac{E t}{\eta})$ predict about stress in polymers?
What is the standard linear solid model composed of?
What is the standard linear solid model composed of?
In the stress relaxation scenario described, what is assumed to be constant?
In the stress relaxation scenario described, what is assumed to be constant?
How does the Voigt model differ from the Maxwell model in terms of element arrangement?
How does the Voigt model differ from the Maxwell model in terms of element arrangement?
What is the significance of the term $\tau_0$ in the equations provided?
What is the significance of the term $\tau_0$ in the equations provided?
In the relaxation equation $0 = \frac{1}{E}\frac{d\sigma}{dt} + \frac{\sigma}{\eta}$, what does the term $E$ represent?
In the relaxation equation $0 = \frac{1}{E}\frac{d\sigma}{dt} + \frac{\sigma}{\eta}$, what does the term $E$ represent?
What is the result of integrating the equation for stress relaxation?
What is the result of integrating the equation for stress relaxation?
Which model provides a better representation of real polymer behavior under stress relaxation conditions?
Which model provides a better representation of real polymer behavior under stress relaxation conditions?
Flashcards
Viscoelastic Material
Viscoelastic Material
A material that exhibits both elastic and viscous properties, meaning it deforms under stress and recovers partially over time.
Maxwell Model
Maxwell Model
A simplified representation of a viscoelastic material, consisting of a spring (representing elastic behavior) and a dashpot (representing viscous behavior) connected in series.
Creep
Creep
The ability of a material to deform under stress and remain deformed after the stress is removed.
Stress Relaxation
Stress Relaxation
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Modulus (E)
Modulus (E)
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Viscosity (η)
Viscosity (η)
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Elastic Deformation
Elastic Deformation
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Viscous Deformation
Viscous Deformation
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Total Stress in Composite Material
Total Stress in Composite Material
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Voigt model
Voigt model
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Creep Behavior in Voigt model
Creep Behavior in Voigt model
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Voigt model and Stress Relaxation
Voigt model and Stress Relaxation
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Standard Linear Solid
Standard Linear Solid
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Combined Creep and Stress Relaxation
Combined Creep and Stress Relaxation
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Advantages of Standard Linear Solid
Advantages of Standard Linear Solid
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Creep Rate
Creep Rate
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Relaxation Time (τ0)
Relaxation Time (τ0)
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Maxwell Model for Stress Relaxation
Maxwell Model for Stress Relaxation
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Voigt Model (Kelvin Model)
Voigt Model (Kelvin Model)
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Study Notes
Viscoelastic Mechanical Models
- Viscoelastic materials exhibit stress and strain dependence on time.
- Ideally, stress relaxation is predictable from creep data, but this is difficult with real polymers.
- Viscoelastic materials are often modeled as linear viscoelastic, assuming independent elastic and viscous components.
- Deformation is described via a combination of Hooke's law (elastic) and Newton's law (viscous).
- These models only apply to small strains.
Mechanical Models
- Mechanical models use elastic springs (Hooke's law) and viscous dashpots (Newton's law).
- Different model combinations are used to represent viscoelastic behavior.
- Maxwell model: spring and dashpot in series.
- Voigt model: spring and dashpot in parallel.
- Standard linear solid: Maxwell element and spring in parallel.
Maxwell Model
- Consists of a spring and dashpot in series.
- Overall strain is the sum of the strain in the spring and dashpot (e = e₁ + e₂).
- Stress is the same across the elements.
- From Hooke's and Newton's law, the stress-strain relationship during constant stress involves an exponential decay of stress with time, which is a better description of polymer behavior than the Maxwell model for creep.
- Describes stress relaxation better than creep behavior for polymers.
Voigt Model
- Consists of a spring and dashpot in parallel.
- Strains in parallel elements are uniform: e = e₁ = e₂.
- Stresses add to give an overall stress (σ = σ₁ + σ₂).
- This model is useful for describing creep behavior, where stress is held constant.
Standard Linear Solid
- Combines Maxwell and Voigt elements in a parallel arrangement (e.g., with an additional spring)
- This enhances a description of a polymer's response including stress relaxation and creep behavior.
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