Resonant ultrasound spectroscopy and non-destructive testing

The use of mechanical resonances to test properties of materials is perhaps older than the industrial revolution. Early documented cases of British railroad engineers tapping the wheels of a train and using the sound to detect cracks perhaps mark the first real use of resonances to test the integrity of high-performance alloys. Attempts were made in the following years to understand the resonances of solids mathematically, based on the shape and composition. But Nobel Laureate Lord Rayleigh best summarized the state of affairs in 1894, stating {open_quotes}the problem has, for the most part, resisted attack{close_quotes}. More recently, modern computers and electronics have enabled Anderson and co-workers with their work on minerals, and our work at Los Alamos on new materials and manufactured components to advance the use of resonances to a precision non-destructive testing tool that makes anisotropic modulus measurements, defect detection and geometry error detection routine. The result is that resonances can achieve the highest absolute accuracy for any dynamic modulus measurement technique, can be used on the smallest samples, and can also enable detection of errors in certain classes of precision manufactured components faster and more accurately than any other technique

New approaches to thermoelectric cooling effects in magnetic fields

The authors review thermoelectric effects in a magnetic field at a phenomenological level. Discussions of the limiting performance and problems with its computation for both Peltier and Ettingshausen coolers are presented. New principles to guide the materials scientists are discussed for magnetic effects, and a brief review of the subtle measurement problems is presented

New directions in materials for thermomagnetic cooling

The authors review thermoelectric effects in a magnetic field at a phenomenological level. Discussions of the difficulties in computing the limiting performance for both Peltier and Ettingshausen coolers are presented. New principles are discussed to guide the materials scientist in the search for better Ettingshausen materials. These principals are based on the tensor transport and solid state electronic properties of Bi{sub 1{minus}x}Sb{sub x} alloys. A brief review of the subtle measurement problems is presented