Evaluation of Internal Cracks and Collapse in Poplar Wood (Populus nigra) during a Conventional Drying Process with Ultrasonic Inspection

Saeid Eshaghi,Mahdi Shahverdi,Hadi Dashti

doi:10.15835/nsb427412

Abstract

In this research, internal cracks and collapse of wood, formed during drying process, were measured using ultrasonic inspection. For this purpose, seven poplar (Populus nigra) small blocks were dried, according to a time-based schedule. Ultrasonic waves’ propagation velocity was measured at both parallel and perpendicular to grain directions, using Sylvatest ultrasound device, during kiln drying process. Results showed that in all dried blocks, waves’ propagation velocity in the parallel direction was higher than in the perpendicular direction to grain. Ultrasonic waves’ propagation test for non-destructive identification of internal cracks, which occurs in wood during drying process in the parallel direction, was more successful compared to the perpendicular direction. Using ultrasonic waves’ propagation test for detection of collapse that occurs in wood during drying process was not useful.

Highlights

Ultrasonic test is a method with old history, which previously was used for predicting the condition of substances
The samples for 36 hours were exposed to 82°C dry-bulb temperature and relative humidity (RH) of 50%
Waves’ propagation velocity in parallel direction varied within range of 3500-4000 m/s and in perpendicular direction, in contrast, values were within the range of 800-1500 m/s

Summary

Introduction

Ultrasonic test is a method with old history, which previously was used for predicting the condition of substances. Ultrasonic test is able to detect both internal cracks and collapse of a piece but it does not mean that this technique is necessarily the best method for all inspection cases. Selection of the best method depended on the type of existing defect, shape and size of the test samples. For detection of internal flaws, ultrasonic techniques were vastly employed but they could be used for revealing small superficial cracks as well. Almost all the non-destructive testing methods, used for different materials and products were applicable for wood and wood composites. Selection of the method depends on the application. For decisiveness in quality of wood products, as an accurate and quick technique, a non-destructive method could be used. Ultrasonic wave’s propagation as a simple, low-cost and flexible method has application for assessment of wood and wood product properties

Methods

Results

Conclusion