ABSTRACT

VII. Thick Plate Wave Measurement Techniques 298

VIII. Out-of-Plane Measurement Techniques 299 A. Introduction 299 B. Transduction 302 C. Instrumentation 305

IX. Miscellany 307

References 308

I. INTRODUCTION

I plan to examine ultrasound in paper within a limited scope. I will review in-plane and out-of-plane ultrasonic diagnostics of paper. I will outline the mechanics under­ lying these techniques. I will conjecture on physical meaning. I will address issues of experimental difficulty, and I will compare techniques. To my knowledge, there is no other unified exposition of these important topics as applied to paper. I believe this leaves me an opening for a contribution. On the other hand, I do not include onmachine measurements. I omit the influences of papermaking variables on ultrasonic velocity and the relationships between ultrasonic stiffnesses and other physical prop­ erties. I will not talk about ultrasonic processing in the pulp and paper industry. These subjects are adequately entertained elsewhere. I acknowledge that my nar­ rowed perspective excludes important works that would be referenced in a more even account of ultrasound in paper. I rationalize my convenient lapses by appeal to the charge of the book. The objective of these volumes is to critique experimental meth­ ods. The intent is not to emphasize papermaking or paper physics.