History, present state and future of non-destructive testing for wood.

The Non-Destructive Testing(NDT),that does not damage the tested object and influence its performance,is an effective method,where various physical principles and chemical phenomena are involved.Its advantages include short measuring time,simple method,high stability,no destruction and capability of working in continuous production.It has been widely used in the field of wood science and engineering.In this paper,the mechanical properties of wood are studied by non-destructive testing and the wood is graded by wood strength.Different non-destructive testing methods are compared in the tests of mechanical properties,and their importance is shown in wood utilization,production costs and production efficiency.An review of the history,the present state,and the future development of NDT is given.