1.5 - solids under stress Flashcards
(22 cards)
What are polymers?
Long chains of atoms entangled together.
What are crosslinks?
Connections between polymer chains that affect their properties.
What are Van der Waals bonds?
Weak interactions that are easy to break.
True or False: Van der Waals bonds require stress to break.
True.
What happens to Van der Waals bonds under high stress?
They can break between chains, requiring relatively high stress.
Fill in the blank: Polymers consist of long chains of atoms that are ______.
[entangled together].
What is the relationship between stress and strain in polymers?
High stress is needed to break Van der Waals bonds and induce strain.
What are the characteristics of weak solids?
Brittle
Weak solids have low structural integrity, making them susceptible to failure under stress.
What occurs during the AB phase of stress-strain behavior?
Long chain molecules unravelling and straightening
This phase requires relatively low stress to initiate the alignment of molecular chains.
What happens during the BC phase of stress-strain behavior?
Long chains fully aligned and covalent bonds are being stretched
This phase requires high stress to cause strain, indicating that the material is nearing its limits.
What does the CD phase represent in the stress-strain curve?
Work done as rubber contracts, returning to its original length
This phase indicates the elastic behavior of the material, showcasing its ability to return to the original state after stress is removed.
What does the EF phase signify in the stress-strain relationship?
“Permanent set” due to overstraining
This occurs when a material is stretched beyond its elastic limit repeatedly, leading to a permanent change in its natural length.
Fill in the blank: During the AB phase, relatively ______ stress is required.
low
This indicates that materials can begin to deform with minimal applied forces.
Fill in the blank: The stress measured in Nm² represents ______.
internal forces within a material
Understanding stress is crucial for determining how materials will behave under various loads.
True or False: High stress is required to cause strain when long chains are fully aligned.
True
This reflects the increased resistance of materials as they reach their limits.
What does the Hysteresis Loop represent?
Difference in work done during loading and energy recovered during unloading
The Hysteresis Loop illustrates the energy dynamics in materials subjected to cyclic loading.
What happens to energy during one cycle in a hysteresis loop?
Energy is lost
This loss is due to the internal energy increase of the molecules when stretched.
What causes a permanent change in the length of rubber?
The application of force or load
Permanent deformation occurs when the elastic limit is exceeded.
What is released as heat during the stretching of a band?
Excess energy
This energy is a result of increased internal energy of the molecules.
Fill in the blank: The Hysteresis Loop explains the difference in work done during _______ and energy recovered during unloading.
loading
True or False: The energy lost during one cycle is completely recovered.
False
Some energy is converted to heat and is not recoverable.
What structural category do springs belong to?
Structure of solids
Springs are a type of solid material that can deform under load.
