Opening Up to the Outside World: A History of Public Health in China

Predicting the material properties of wood through nondestructive evaluation (NDE) techniques is a matter of considerable importance for the timber industry. NDE techniques can significantly increase the accuracy of grading of wood compared to visual grading methods. Longitudinal stress wave and transverse vibration nondestructive evaluation techniques have proven to be accurate means of evaluating the quality of wood-based products. Researchers have found strong relationships between stress wave and transverse vibration parameters (e.g., wave velocity and predicted modulus of elasticity) with the actual static bending properties (e.g., modulus of elasticity and modulus of rupture) of dry as well as green wood-based materials [1–3]. Therefore, these NDE techniques can be used to presort or grade structural wood prior to drying. Discarding wood with inferior properties prior to drying can result in significant cost savings in the drying process

In situ assessment of structural timber using stress-wave measurements

This paper summarizes the test recommendations for in situ assessment of structural timber using stress wave measurements as developed by members of the RILEM Technical Committee AST 215 "In-situ assessment of structural timber". In the first part, the basic principles, the equipment, and the practical application of stress-wave-based testing using the time-of-flight method are described. A detailed testing procedure provides hands-on information on the execution of in-field stress wave testing. A typical example is given to demonstrate step-by-step on how to evaluate stress wave readings and the health state of the inspected timber member. The latter part of the paper gives a short overview of the use of acoustic tomography and ultrasonic echo methods