Measuring strength of materials (most often, wood), isn’t just about pushing the material to the point of failure. Instead, to measure strength in a way that helps achieve exceptional final product, strength must be considered in terms of five basic properties:
Then, considering elasticity (E), or the amount a piece of lumber will deform in proportion to an applied load under elastic range stresses, the considered properties work together to provide us with a measure of strength. We take it a little further than that. By utilizing the frequency of sound in the board after an impact, it’s length, density, and moisture content, we determine the dynamic E (Edyn).
Measuring Edyn along with routine testing of static E (Estat) is what allows us to gather the data needed to classify boards into predefined machine stress rated (MSR) grades, and thus help streamline and optimize your manufacturing process.
By measuring the modulus of elasticity, we can separate the strong boards from the weak boards in the manufacturing process and allow engineers to build within their required and regulated design codes. Lumber that has been evaluated for Edyn are referred to as Machine Stress Rated (MSR) and are grouped into four main classes: 1650-1.5E, 1800-1.6E, 2100-1.8E and 2400-2.0E. These boards of predicted stiffness then become the components for structural elements in building like roof trusses and more recently, glulam beams and cross laminated timber panels for mid-rise wooden building or mid-rise hybrid buildings.
In most markets, there’s a premium price built in to MSR lumber as opposed to visually inspected lumber. When lumber is MSR rated, the purchaser knows that each board will meet the structural requirements, whereas visually inspected boards may need knots or other natural defects cut out.
Building with wood of known strength properties has allowed architects and engineers to specify wood structural elements in commercial buildings spanning large distances without sagging or bending. With the recent acceptance of CLT panels in local building codes, mid-rise and high-rise building are starting to gain acceptance in North America. Wood elements in buildings impart natural and warm characteristics which provide a calming work environment. Since wood is a natural carbon sink, the life cycle impact on the environment of wooden buildings is much lower than equivalent building built with steel or concrete.
By measuring for strength to MSR-rated quality standards, our sensors allow you to not only carefully monitor the parts of your process that account for moisture, but also offer a wider range of buyers for your final lumber product. Add in the bonus of premium prices that increase your profits, and the choice becomes clear.
Precigrader is an acoustic on-line strength grading system that uses a spring-loaded impact mechanism that strikes the lumber as it passes. The resulting vibration is captured by microphones to determine the appropriate MSR grade.Learn More