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Use of rapid prototyping technology in complex plastic structures. Part I. Bench testing and numerical calculations of deformations in harmonic drive made from ABS copolymer

Pacana Jacek, Oliwa Rafał

Polimery

2019

T. 64, nr 1

56--62

Z wykorzystaniem metody cyfrowej korelacji obrazu (DIC) przeprowadzono pomiary odkształceń 3D koła podatnego zębatej przekładni falowej. Badania wykonano przy użyciu modeli fizycznych wytworzonych z zastosowaniem druku 3D z kopolimeru ABS, zapewniającego wystarczającą nośność i sztywność modelu. Uzyskane w badaniach stanowiskowych wartości odkształceń koła podatnego porównano z wynikami obliczeń przeprowadzonych z zastosowaniem metody elementów skończonych (MES). Wykazano dużą zbieżność otrzymanych wyników, jednak odkształcenia zmierzone na modelu rzeczywistym charakteryzują się większą nieregularnością niż odpowiadające im rozwiązania uzyskane metodą numeryczną. Wyniki otrzymane w pomiarach optycznych wskazują na zasadność stosowania w badaniach stanowiskowych prototypów przekładni zębatych modeli fizycznych wykonanych z tworzyw polimerowych z wykorzystaniem technologii szybkiego prototypowania.

In the study, measurements of 3D deformations of the flexspline in harmonic drive were performed by applying a digital image correlation (DIC) method. The tests were carried out with the use of physical 3D printed models made of ABS copolymer (acrylonitrile-butadiene-styrene), which ensured sufficient capacity andrigidity of the structures. The findings related to deformations in flexspline, obtained through bench testing, were compared to the results of calculations conducted using the finite element method (FEM). Significant convergence in the findings obtained using the two methods was shown, yet deformations measured in the real-life model were characterized by greater irregularity compared to the corresponding solutions obtained with the numerical method. The results obtained through optical measurement confirm that physical models made of plastics, built using rapid prototyping technology, can justifiably be appliedin bench testing of prototype gear transmissions.

Evaluation of true stress in engineering materials using optical deformation measurement methods

Bogusz P., Popławski A., Morka A., Niezgoda T.

Journal of KONES

2012

Vol. 19, No. 4

53-64

The aim of the paper is to evaluate a method of determining true stress in the steel sample subjected to static axial tensile on a universal testing machine. The tensile specimens were made of steel ST3, which was chosen because of its relatively high plastic deformations. Strain measurement was performed using traditional extensometers and additionally a non-contact optical deformation measuring system. Material properties were obtain by the extensometer measurements. The optical equipment registered the investigated sample through the optical system composed of two cameras and calculated a three-dimensional model of the material deformation in time. Displacement fields in axial and radial directions were determined with Digital Image Correlation method (DIC). Then the logarithmic axial strain map and radius shrinkage map in the area of the neck were obtained. Characteristic dimensions of the neck: curvature and width were also measured. It allowed determination of cross-section area changes in the real time, and in the result, calculation of actual true stress in the material during failure process. In this case Bridgman's and other scientists' formulas of stress distribution in the neck were applied. A numerical model, where material properties of finite elements were described by the Johnson-Cooke material model, was developed in LS-PrePost software. The FEM model was computed in LS-DYNA solver. The output tensile curve and neck curvature radius were compared with relevant data obtained from the optical measuring system.