Numerical and experimental validation of a theoretical model for bimaterial helical springs

Abstract

This article deals with the numerical and experimental validation of a theoretical elastic model for bimaterial helical springs developed by the authors in a recently published article. The numerical validation is performed on finite element models involving one half turn of several springs identified by three spring indices (c=D/d= 3, 5, 10) and three section types (solid homogeneous, solid bimaterial and thin hollow). The experimental validation involves compression tests on two polymer (acrylonitrile butadiene styrene) spring configurations produced by rapid prototyping and cladded by ionic infiltration with CrNiCo alloy. For the larger prototype spring, the stresses are measured on the outside of the coil by means of miniature strain gauges. The numerical results confirm the theoretical stress concentration factors within an error of 5%. The experimental results closely agree with the predicted spring rates of all springs, either fully polymeric or bimaterial. In addition, the strain gauge measurements on the instrumented spring correlate well with the theoretical stresses calculated for that particular geometry

Formulation of a three-dimensional shear-flexible bimaterial beam element with constant curvature

“…The paper by Dragoni and Bagaria 4 provides the force–deflection curve for an axially loaded cylindrical helical spring with N = 4.5 coils, mean coil diameter D = 50 mm ( R = D /2 = 25 mm) and bimaterial section defined by r i = 3 mm, r o = 3.3 mm ( b = r i / r o = 0.909), E i = 1300 MPa, E o = 35,600 MPa, ν i = ν o = 0.3, G i = 500 MPa, G o = 13,692 MPa, ( χ = E i / E o = G i / G o = 0.0365).…”

“…The process is particularly suited for improving the mechanical performance of shell-like structures and is finding its way in the automotive, aerospace, medical and sport industry. The authors have recently explored the application of this technology to polymer helical springs, 3,4 showing potential for obtaining hybrid springs as light as the polymer core and as strong as the nanometal cladding. Dragoni and Bagaria 3,4 have developed ad hoc analytical equations to deal with the axial loading of simple cylindrical helical springs.…”

“…The authors have recently explored the application of this technology to polymer helical springs, 3,4 showing potential for obtaining hybrid springs as light as the polymer core and as strong as the nanometal cladding. Dragoni and Bagaria 3,4 have developed ad hoc analytical equations to deal with the axial loading of simple cylindrical helical springs. More generally, plastic-wire springs manufactured with complex geometries (as shown in Figure 2 for metal springs) could offer advantages if augmented with the nanometal cladding.…”

Evaluation of Energy-Based Model Generated Strain Signals for Carbon Steel Spring Fatigue Life Assessment

“…For example, equivalent stiffness and stress relationship of coil spring was developed to approximate the multi-axial loadings, where strain and stress had a relationship referring to the elastic modulus [26]. This could be observed through a stress-strain analysis of coil spring using bi-material [27,28]. The analysis proposed the strain and displacement relationship of coil spring where the concept of potential energy was used.…”

Designing novel multilayered nanocomposites for high-performance coating materials with online strain monitoring capability

“…[51][52][53] Another possible application is as a nanometal coating for polymer springs as exemplified by the work of Dragoni and Bagaria. 54,55 The Cu-Nb nanolayer coating strengthens and stiffens the polymer core of the spring and behaves as an in situ strain monitoring tool while in operation.…”