Dynamic Systems Limited

Norman A Lindeman

David E Ferguson

David Ferguson

A jack assembly, for use in a materials testing system, utilizes both a cam and a resilient push block. The cam, having an progressive eccentric, is situated between the push block and a jaw housing and located partially within a corresponding shallow channel in each such that both channels effectively straddle the cam. The channels accommodate axial rotation of the cam. The push block is formed of a material with an appropriate modulus of elasticity such that bending moments, particularly at ends of the push block and resulting from axial rotation of the eccentric to its top dead-center position, cause the channel in the push block to elastically deform and increasingly and sufficiently deflect against and around the eccentric, thus increasingly pinching the eccentric and securely locking the cam, push block and specimen grip in their proper positions.

Apparatus for a cam-based jack assembly for use in materials, testing machines and an accompanying method for use therewith

A specimen grip assembly which can be used with a relatively light-weight jaw in a materials testing system. The specimen grip assembly illustratively contains a grip shell and a pair of wedge-shaped specimen grips. The shell has a truncated, frusto-pyramidal exterior shape with two outwardly facing inclined surfaces, both inclined at an angle and which matingly abut and slide against complementary inclined interior surfaces of the jaw. The grips are oriented in a recess within the shell such that inclined surfaces of the grips abut against interior complementary surfaces of the shell. The shell, containing the grips and specimen, is suitably positioned within the jaw, with the shell and grips then jacked into a fixed position. The shell substantially eliminates any noticeable compliance from the specimen grips that might otherwise arise from tensile and/or compressive forces applied to the jaw and specimen grip assemblies during a test program.

Specimen grip, having a grip shell, for use in a materials testing machine

A technique for imparting direct resistance heating to a gauge length of a conductive metallic specimen under test and which can be used to add an independent dynamic thermal capability to a mechanical material test system. Specifically, a pair of, e.g., conductive collars, each of which encircles and abuts against a corresponding portion of the external surface of the specimen near an opposing end of its gauge length and inward of a corresponding grip. Each collar imparts additional self-resistive heat to the specimen along a circumferential collar/specimen interface. This additional heat appreciably reduces or cancels thermal gradients otherwise arising from self-resistive heating across the gauge length as well as compensates for thermal losses in each specimen end section. Through this arrangement, each specimen end section and the grips are not appreciably heated as the gauge length heats. The amount of additional heat is set by selecting a collar material to have a desired resistivity and also by appropriately dimensioning each collar.

Technique for applying direct resistance heating current to a specific location in a specimen under test while substantially reducing thermal gradients in the specimen gauge length

Apparatus and an accompanying method for use in a conventional dynamic material testing system to advantageously provide enhanced self-resistive specimen heating. Specifically, a fixture () is added to the system. The fixture has two supporting arms (), each holding one of two opposing and conductive anvil assemblies (). The fixture applies adequate force to each arm sufficient to hold a specimen () in position between the anvil assemblies and establish a good abutting electrical contact between the specimen and each assembly but without exerting enough force to deform the specimen as it is being heated. Separate opposing and existing coaxially-oriented shafts () controllably strike both arms and move the anvils together, hence squeezing the specimen and generating each deformation therein. Electrical heating current is controllably applied through the support arms, the anvils and the specimen in order to self-resistively heat the specimen in a predefined temporal manner with respect to the specimen deformations.

Apparatus for providing enhanced self-resistive specimen heating in dynamic material testing systems and accompanying method for use therein

Apparatus for use in a conventional dynamic material testing system to advantageously provide uniform self-resistive specimen heating with enhanced temperature uniformity. Specifically, an anvil stack () in an anvil assembly () has a foil interface () with a composite layer () containing, e.g., a concentrically oriented multi-component arrangement formed of an inner high strength and insulating disk () and an outer ring-shaped resistive region (), situated between an anvil base () and an anvil top (). An insulating member () electrically and thermally insulates all sides of the anvil stack from its supporting structure.

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Sand Lake, NY, United States of America

Norman A Lindeman