Patent GB-600271-A (GB)
Title: Improvements in machines for fatigue testing of materials
IPC: G01N3/34
Filed: 1945-04-04
Abstract: 600,271. Fatigue testing of materials. GROUPEMENT FRANCAIS POUR LE DEVELOPPEMENT DES RECHERCHES AERONAUTIQUES. April 4, 1945, No. 8362. Convention date, May 22, 1942. [Class 106 (ii)] A machine for fatigue tests-on materials comprises jaws for gripping one end of a test piece, a beam pivotable about an axis, and means for imparting an oscillating motion to the beam, the latter terminating at one end in a forked member adapted to engage a roller which is rotatable about an axis and supported by a member secured to the free end of the test piece. Uniform, variable and spasmodic stresses can be induced in the test piece. As shown in Fig. 2, the machine comprises a frame 13 provided with clamps 33, 34 for the specimen 11, the latter having secured to its free end a yoke 37 carrying a roller 10 lying between the forkedend 9 of a beam 5. The beam is pivoted at 6, and adapted to be oscillated by an adjustable rod 4 pivoted at one end at 30 on the beam and at the other end at 22 on a slide adjustable in a slotted crank-plate 3. The plate 3 is secured to a shaft 15 (not shown) rotated by a belt-and-pulley arrangement from a motor I and provided with a counter. An indicator 7 secured to the beam 5 co-operates with a fixed scale 8 to indicate the movement of the beam. The motor is stopped automatically on fracture of the specimen by an arrangement comprising a switch 42 which is opened on the depression of one end 41 of a lever 39 pivoted at 40 ; the other end 43 of the lever rests on shackle 44 attached to the spindle 45 of the roller 10 and is biassed upwardly by a spring 46, so that when the specimen 11 is broken the roller 10 and lever end 43 are pulled upwardly. By adjusting the eccentricity of the crank-pin 22 and the length of the rod 4, different amplitudes of movement about a number of mean positions can be imparted to the beam 5. An arrangement for determining the force necessary to deflect the end of the specimen 11 through a given distance is incorporated, and consists of a plate, on which weights are placed, carried by a rope adapted to pass over a pulley 47<1> and be attached to the free end of the specimen, a comparator being used to measure the corresponding deflection. In the form shown in Fig. 6, the beam 5 is connected to two connecting-rods 4<1>, 58 at 30 and 6<1> respectively, and a rod 55 pivoted to the frame,at 56 is forked at the other end to engage the pivot 30 of the beam. The two rods 4<1>, 58 are both constructed and operated like the rod 4 shown in Fig. 2. Motors 1, 59 can be operated singly or simultaneously to impart a simple or compound movement to the beam 5, and the movement can be still further modified by varying the speeds of the motors and eccentricities of the crank-pins. If a simple oscillation having superposed spasmodic movements of greater amplitude are desired, the rod 58 can be replaced by a rotating cam against which the pivot end 6<1> is spring-pressed. An arrangement of epicyclic gearing is described and shown whereby either or both crank-pins of the connecting-rods follow an epicycloidal path ; in one case, the gearing to each crankpin is driven by two motors. In a further arrangement, the effective lengths of the connecting-rods can be varied during the test by using pivoted levers. The test specimen, Fig. 4 (not shown), is a flat plate having a flared base with a registering hole therein, a narrower and tapered centre portion, and a flared upper part.