Fundamentals of Materials Science Flashcards
Max occlusal force range
200 to 3500 N
Occlusal forces are higher in the ____ of the mouth
posterior
Forces on 1st and 2nd molars range
400 to 800 N
Force on bicuspids
300 N
Force on cuspids
200 N
Force on incisiors
150 N
Force in children
235-494 N with an average increase yearly of 22N
Patients that have dental prosthetics have an increased or decreased occlusal force?
decreased
100N on molars and bicuspids
40N incisors
in complete dentures
What is stress?
Stress=Force(N)/Area in pascals (Pa)
when a force acts on a constrained body, the force is resisted by the body and the internal reactions is equal in magnitude and opposite in direction to the applied external force and is thus called stress.
Axial Stress (tension)
results from two sets of forces directed away from each other in the same straight line or when one end is constrained and the other is subject to a force directed away from the constraint(tensile stress).
Axial Stress (Compression)
results from two sets of forces directed toward each other in the same straight line or when one surface is constrained and the other is subjected to a force directed toward the constraint.
Shearing stress
occurs from two sets of forces directed parallel to each other, but not along the same straight line
Torsion stess
results from the twisting of a body
bending or flexure
results form an applied bending moment.
Strain
deformation in a body due to stress
Proportional limit
the highest stress at which the stress-strain curve is a straight line, that is strain and stress are linearly proportional. No perm. deformation below/before this point. Object will return to original dimensions.
Elastic region
the region of the stress strain curve before the proportional limit (PL)
Plastic region
anything after the (PL) and the shape will have permanent deformation.
Elastic limit
the max stress that a material will withstand without permanent deformation.
Yield Strength
the stress at which a material deforms plastically and there is a defined amount of permanent strain.
ultimate stensile strength
the maximum stress that a material can withstand before failure in tension
Ultimate compressive strength
the max stress a material can withstand without compression
fracture strength
point at which a brittle material fractures and if the material doesn’t fracture then it’s the point at which necking occurs and reduction of area occurs.
Elongation
the deformation that results from the application of tensile force.
elastic modulus
- the measure of elasticity of a material. -Represents the stiffness of a material within the elastic range.
- the Slope of the linear portion of the Strain-Stress curve.
Ductility
ability to be drawn and shaped into wire by means of tension.
Malleability
ability to be hammered or rolled into thin sheets without fracture
Resilience
resistance of a material to permanent deformation.
- Indicates the amount of energy necessary to deform the material to the PL.
- area of the elastic portion of Stress-strain curve.
Toughness
the RESISTANCE of a material to fracture, is an indication of the amount of energy necessary to cause fracture.
- The area under the elastic and plastic portions of the curve.
- represents the energy required to stress the material to the point of fracture.
Fracture toughness
the ability to be plastically deformed without fracture, or the amount of energy required for fracture.
Stiffness
the extent to which it resists deformation in response to an applied force.
