STRESS AND STRAIN IN WOOD Flashcards
Branch of science concerned with the behavior of physical bodies when subjected to forces or displacement, and the subsequent effects of the bodies on their environment
Mechanics
Wood is considered as an ____________, meaning it has different mechanical properties from its three sections or directions: longitudinal, radial, and tangential.
orthotropic material
- applied forces in wood
stress
- measure the change/deformation of wood length
strain
KINDS OF STRESSES IN WOOD:
a. Compressive Stress
b. Tensile Stress
c. Shear Stress
- A type of stress that develops when a material is subjected to an external force that tends to squeeze or shorten the wood.
Compressive Stress
- reduces the length/dimension of wood
- shorten the wood
- inward
Compressive Stress
- Exerted on a wood if the force tends to increase or to expand the dimension or volume of the wood.
Tensile Stress
- increase/expand volume of wood
- outward
Tensile Stress
- Relevant in situations where forces act parallel to the grain, causing adjacent layers of wood fibers to slide or deform.
Shear Stress
- Result from forces that tends to cause portions of a wood to move or slide in parallel but opposite direction.
Shear Stress
- move or slide parallel to the grain
Shear Stress
- Force acts perpendicular to area of contact
Normal Stress
- Referred to as the change in length per unit of length in the direction of stress.
STRAIN IN WOOD
- Measure of the deformation or change in the shape of the material that results from the applied force.
STRAIN IN WOOD
Stress is usually expressed in ____________ or in pascals (Newton per square meter)
pounds per square inch (psi)
- is referred to as the change in length per unit of length in the direction of stress.
Strain
- Resistance of the wood specimen from being deformed when stress is applied, and a longer line of ______ means it has a greater resistance to deformity.
MODULUS OF ELASTICITY (MOE)
- ability of wood to recover to the original state/form
MODULUS OF ELASTICITY (MOE)
Stress and Strain curve for a wood specimen tested ________
parallel-to-grain
DEFORMATION IN WOOD:
a. Elastic Deformation
b. Total Deformation
- When there is a sudden change in the shape of wood when load/stress is applied but the change is recoverable when stress is removed
- temporary
Elastic Deformation
- It is the line beyond the stress at
proportional limit , where the change in size or shape of the wood when applied with stress is no longer recoverable.
Total Deformation
- the wood specimen applied with load/stress parallel to grain has the capacity to withstand the load until it reaches its breaking point, the amount or intensity of the load that caused the wood specimen to break or fail
MODULUS OF RUPTURE
