Banner for LabNotes
From Lab Notes
Contact Information
Forest Products Laboratory
One Gifford Pinchot Drive
Madison, WI 53726-2398
Phone: (608) 231-9200
Fax: (608) 231-9592


You are here: FPL Home  / Information Products & Services  / Publications

Requested Product

Title: Quantifying knots by image analysis and modeling their effects on the mechanical properties of loblolly pine lumber

Source: European Journal of Wood and Wood Products. 77(5): 903-917.

Author(s)Wright, Stephen ; Dahlen, Joseph ; Montes, Cristian ; Eberhardt, Thomas L.

Publication Year: 2019  View PDF »

Category: Journal Articles
Associated Research Project(s):   FPL-4715-1

Abstract: Automated grading machines that quantify knots are increasingly deployed by lumber mills, however their use in mill studies that assess lumber quality have been limited. The objective here was to develop a method to evaluate the knots of loblolly pine lumber using image analysis and to develop models to predict modulus of elasticity (MOE) and modulus of rupture (MOR) from 171 pieces of dimension lumber. Lumber was photographed on the wide faces and individual knots were identifed using the k-means clustering algorithm. The percentage of wood made up of knots on the wide faces (Knot%) was calculated by summing the individual knot areas over the total surface area, as well as on a sub-section of the lumber span which was optimized separately for MOE (Knot%MOE) and MOR (Knot%MOR). Models were built using the knot measurements and compared to models built using specifc gravity (SG) and acoustic velocity squared (AV2). Knot% explained 30% of the variation in MOE and 39% of the variation in MOR. Incorporating Knot%MOE into a model with SG and AV2 did not appreciably improve model performance (R2=0.75, RMSE=1.1 GPa) over the base SG and AV2 model (R2=0.74, RMSE =1.2 GPa). Incorporating Knot%MOR into a model with SG and AV2 signifcantly improved the prediction (R2=0.65, RMSE =7.2 MPa) compared to the base SG and AV2 model (R2 = 0.56, RMSE = 8.0 MPa). This study demonstrates the feasibility of using image analysis to assess knot information in lumber to improve predictions of mechanical properties.

Keywords: Southern pine; wood quality; specific gravity; knots

Publication Review Process: Formally Refereed

File size: 1,024 kb(s)

Date posted: 09/26/2019

This publication is also viewable on Treesearch:  view
RITS Product ID: 95871

Additional items that might interest you
View the video celebrating FPL's 100 years of public service in 2010, from the producers of the Greatest Good....view

Research Highlights from FPL....view

Termite Eradication: A search for the Holy Grail.... view

Moisture Management in Residential Construction Series videos...view

Wood Floor Systems in Residential Construction Series videos....view
- FPL's Mission and Strategic Plan -

FPL's mission is to identify and conduct innovative wood and fiber utilization research that contributes to conservation and productivity of the forest resource, thereby sustaining forests, the economy, and quality of life. ... ..more »

- FPL Research Emphasis Areas -
Advanced Composites

As an integral part of the FPL mission, we improve the long-term sustainability of our Nation's forests by creating valuable composite products from biobased materials ... ..more »

Advanced Structures

The FPL has been in the forefront of wood-frame housing research since 1910 and has long been recognized as a world leader in such housing-related areas as engineered wood ... ..more »

Forest Biorefinery

We all know the compelling reasons that the United States needs to reduce its dependence on fossil fuels. Historically, the greatest increases in energy demand have been for transportation fuels ... ..more »


A leader in wood products research for over a century, the FPL is positioning itself to become the lead Federal research facility for the application of nanotechnology in forest products ... more »

Woody Biomass Utilization

Forests in the United States contain a substantial amount of small-diameter, overstocked, and underutilized material.FPL research projects are exploring the potential of the small-diameter ... ..more »