engleski

Considerations on the Application of Photoelasticity to Stress Measurement in Compliant Elements

The purpose of the research in this paper is to assess the viability of the application of photoelastic measurements for the material behavior modelling of additively manufactured (AM) compliant elements. Compliant elements alone or as a part of compliant mechanisms gain at least part of their mobility from the deflection of flexible members rather than from movable joints only. They offer a valid alternative to conventional sliding and rolling mechanisms and are used to transfer motion, force and torque and characterised by high precision, possibility of monolithic manufacturing (‘design for no-assembly’) and of parallel kinematics, as well as reduced costs, no backlash and wear. Compliant mechanisms are nowadays widely used in mechanical engineering design, precision engineering as well as technologies for micro and nanosystems. Until the advent of AM, the design and manufacture of elastic elements had been an onerous task. The development of adequate numerical models was required to facilitate the application of AM to compliant mechanisms, and photoelastic testing presents a fast method for the verification and evaluation of such models with regard to stress and strain of specific mechanism geometries fabricated from transparent polymers. Until now, photoelastic specimens have been printed using stereolithography and polyjet technology, however technological advances have made digital light processing (DLP) techniques a faster and more precise alternative. The application of photoelastic testing to estimate the properties of AM materials was investigated concurrently with the possibility of using specific geometries. The efficiency, accuracy, and applicability of photoelastic testing on transparent polymeric DLP produced samples was determined with three-point bending tests performed on rectangular bar specimens, while bending hinge specimens were tested flexurally. The applicability of photoelastic testing to different types of materials was verified through photoelastic constant determination, stress-strain response in three-point flexural tests and stress-strain response in cantilever flexural tests. Usable images were recorded and analysed, therefore proving that fast qualitative solutions can be provided by photoelastic testing.

Photoelasticity ; Compliant Elements ; Material Behavior

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