Definition Of Modulus Of Elasticity
Modulus of elasticity is also known by another name which is Young’s Modulus. It measures deflection of stress along an axis.
This axis will be either longitudinal (parallel to the grain), radial (perpendicular to the grain), or tangential (perpendicular to the grain and tangent to rings).
Calculating Modulus Of Elasticity
I strongly recommend reading this document to better understand how this modulus is calculated and how formulas are validated. It was written by Jen Y. Liu and Lester H. Floeter.
Layman Understanding For Modulus Of Elasticity
In layman’s terms, modulus of elasticity will measure how far a material such as wood can accept stress and deflect it. To deflect means that once the stress is removed it will return to its original shape.
This is called non-permanent or elastic deformation.
Beyond this point is where the wood would be permanently deformed once the stress if removed. This is called the “plastic region”.
These measurements are not related to rupture as they do not allow the stress to reach the point where a break would occur. Rather the purpose of modulus of elasticity is to measure stress, deformation, and maintain structural integrity.
How Is Modulus Of Elasticity Expressed?
Modulus of Elasticity is expressed as pounds of force per square inch lbf/in2 . You can also find it measured by gigapascals GPa .
The measurements you find with these expressions will assume that the wood has been dried to a 12% moisture content. Any other variation of moisture the measurement will not be accurate.
Why Is This Modulus So Important?
Modulus of elasticity is a critical component to understand load bearing and is an element of that concept. Specifically for this modulus it pertains to stress being applied and then removed.
Logically within construction, engineers will utilize these measurements in order to maintain structural integrity. Within wood art we must know its basics in order to create standing art, mobiles and sculptures, that will last through time.
Important Characteristics To Know About Wood With Young’s Modulus
The numbers you can find on different wood species that pertain to modulus of elasticity may not be consistent from board to board. This will be true even when using the same species, cut, and dimensions.
Why is this the case? There can be other factors that will come into play which impact how wood responds to stress.
Knots within the wood are a weak point that can reduce elasticity. Splits in the wood grain is another example. Thus, more than moisture can impact accuracy.
Grain direction for boards of alternate varieties such as spalted wood will also be different. These differences are very important to note as they will impact the outcome of your project.
Variables will alter the stress strain curve thus compensation could be needed. This compensation could come in the form of added support or thicker wood to support the stress.
Ensure that you make allowances for these additional variables if you intend on utilizing wood with these characteristics. It may be required that you perform tests in order to verify the modulus on the wood you are working with.
Uses Of Modulus Of Elasticity In Woodworking
Within common woodworking, crafting, and wood art there are many applications that can be found to this modulus. Furniture making is one of the more common found with large objects like tables.
Wood mobile art or sculpted art is another common use for this modulus. Generally speaking anywhere that the wood would support applied stress it will be a fundamental element to the creation.
Small objects which will not be having stress or loads applied to them need not worry about this modulus. Nevertheless, simple accents such as shelving in a home can require its consideration.
This modulus can also come in handy for wood artists that manipulate wood by bending. Knowing the point of elasticity to where it becomes deformed “plastic” in a permanent state is beneficial.
We can apply the needed stress in order to shape the wood without reaching the point of rupture or breaking. Adding moisture, steam bending, is a further example of manipulating this property in order to achieve the result.
Our ability to calculate how must stress is needed will grant favorable and repeated success across time. Likewise it can also prevent unwanted deformation and future rupture under loads.