Alternating Bending Fatigue Machine- Engineering Lab Training Systems

Features Self-contained Bench-mounted Fully guarded Digital readout of revolutions to failure Determination of gauge factor Motor stops when specimen fails Specimens from strips of plastics or metals Special setting details supplied Optional extra for rotating fatigue Three year warranty Range of Experiments Bending fatigue of a cantilevered strip of metal or plastic in modes varying from alternating to fluctuating stresses The accessory HSM20X allows an introductory study of fatigue using a Wohler rotating fatigue test, including time to failure caused by various stress levels and materials Description To extend the range of fatigue testing to strips of plastic or metal, this variant of the popular rotating fatigue machine HSM19 has been developed. Using the drive mechanism and base plate of the new HSM19 Mk.3 with a heavy steel portal straddling the width of the base an alternating displacement can be imposed on the free end of a cantilever. The frequency of the reciprocating force is around 24Hz for plastics or 100Hz for metals. A rotating faceplate carries an adjustable eccentric bearing driving a connecting rod attached to the cantilever. The bridge to which this test piece is clamped can be adjusted vertically so that the imposed displacement can be varied. A counter with a 50:1 reduction gear is driven by the electric motor, offering a 1:100 or 1:25 count depending on the drive ratio to the faceplate. Microswitches detect failure of the specimen and stop the motor. To test a specimen a special dial gauge enables a calculated deflection to be set for the actual maximum bending stress of the specimen. An instruction manual containing a set of nomograms is provided to assist the user. Great care has been taken to minimise extraneous vibration. All moving parts are shielded within a protective cover which can be removed during setting up. A guard surrounds the connecting rod to prevent damage when the specimen breaks. It is possible to add extra parts (HSM20X) to this machine so that the rotating fatigue test can be carried out as an alternative. This equipment is part of a range designed to both demonstrate and experimentally confirm basic engineering principles. Great care has been given to each item so as to provide wide experimental scope without unduly complicating or compromising the design. Each piece of apparatus is self-contained and compact. Setting up time is minimal, and all measurements are made with the simplest possible instrumentation, so that the student involvement is purely with the engineering principles being taught. A complete instruction manual is provided describing the apparatus, its application, experimental procedure and typical test results.