Method for evaluating the resilience of a welded assembly and corresponding analysis apparatus measuring the speeds of ultrasonic surface waves

#The invention relates to a method for evaluating the resilience of a welded assembly, together with a measuring device applicable to this method and applied to the measurement of speeds of ultrasonic surface waves.

#The resilience of a mechanical part is the energy required to rupture it. It can be evaluated by tests carried out on test pieces representative of the assembly and respecting certain standards in specialised instruments like the Charpy machine. It is evident that the manufacture of test pieces and the utilisation of a machine are restricting and that methods more easy to apply, in particular non-destructive monitoring through which the resilience could be evaluated indirectly, would be advantageous.

#Such an indirect method for evaluating resilience has been designed and is the aim of this invention. It rests on using ultrasonic surface waves and is applied to a special family of parts: welded assemblies, in particular without addition of material, by diffusion or by analogous methods, of a somewhat thin sheet on a substrate which can be another sheet or a thicker part.

#The invention will now be described referring to the figures, in which:

#FIG. 1 is a general view of the machine used,

#FIG. 2 is a record of measurements,

#The machine used comprises a frame 1 able to be composed of a vertical suspension column 2 at a fixed point 3 and a guideway 4 linked to the column 2 through the intermediary of a slide 5 able to be fixed at a determined place on the column 2 by a pressure screw 6. Two pointers 7 and 8 are placed on opposite sides of the guideway 4 and can be kept in place by pressure screws 9 and 10. Each of them has a measuring head, referenced respectively 11 and 12, and whose essential element is an ultrasonic sensor 13 for the first and a reflector 14 for the second. The heads 11 and 12 are mounted on the pointers 7 and 8 by horizontal pivots 15 and 16, parallel to each other and perpendicular to the direction of the guideway 4, and they are provided with toothed sectors 17 and 18 forming racks engaging with worm screws 19 and 20 operated by adjusting handles 21 and 22 attached to the pointers 7 and 8 so that the heads 11 and 12 can be set at the chosen inclinations, but opposite to each other so that the sensor 13 and the reflector 14 are pointed in descending and converging directions. Other fixation screws 23 and 24 for blocking the heads 11 and 12 on the pointers 7 and 8 make it possible to stop unwanted rotations of the toothed sectors 17 and 18 relative to the pointers 7 and 8 when the desired inclination has been reached. Finally, a flywheel 43 placed under the slide 5 makes it possible to turn the guideway 4 in a horizontal plane.

#In the embodiment illustrated here, the sensor 13 is assigned both to emit ultrasounds and to collect the echoes, as is often the case in this technique, and the reflector 14 is assigned to produce these echoes; meanwhile it is possible to replace the reflector 14 by a pair of sensors in a way described below without the measuring principle being modified.

#The machine overhangs a measuring tank 25 partially filled with water, in such a way that the sensor 13 and the reflector 14 are partially immersed and so that the ultrasonic waves used do not exit from the liquid; the part being studied by the machine is a welded assembly 26, composed of a fairly thin metal sheet 27 set on top, facing the sensor 13 and the reflector 14, and of a substrate 28 which can be another metal sheet or a thicker part. The soldered assembly 26 is set on blocks 29 at the bottom of the tank 25.