Visualization method for stress-field evolution during rapid crack propagation using 3D printing and photoelastic testing techniques

Yang Ju,Feng Gao,Lingtao Mao,Xi Zhao,Yongliang Wang,Heping Xie,Fu-Pen Chiang,Zhangyu Ren,Jiangtao Zheng

doi:10.1038/s41598-018-22773-0

Yang Ju, Feng Gao + Show 7 more

Open Access

https://doi.org/10.1038/s41598-018-22773-0

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Abstract

Quantitative visualization and characterization of stress-field evolution during fracture rapid growth is critical for understanding the mechanisms that govern the deformation and failure of solids in various engineering applications. However, the direct capture and accurate characterization of a rapidly-changing stress field during crack propagation remains a challenge. We report an experimental method to quantitatively visualize and characterize rapid evolution of the stress-field during crack propagation in a transparent disc model containing a penetrating fusiform crack. Three-dimensional (3D) printing technology and a stress-sensitive photopolymer resin were adopted to produce the disc model and to alleviate the residual processing stress that usually blurs the dynamic stress field due to overlap. A photoelastic testing system that synchronized a high-speed digital camera and a pulsed laser with a nanosecond full width at half maximum (FWHM) was used to capture the rapid evolution of the stress field in the vicinity of crack tips. The results show that the proposed method is suitable to directly visualize and quantitatively characterize the stress-field evolution during crack rapid propagation. It is proved that the crack propagation velocity is strongly governed by the stress field around the crack tips.

Highlights

Load-induced stress fields govern the deformation and fracture behaviour of solids
In contrast to the previous investigations[33] that adopted a bonded disc model using two identical pieces of polyester resin with an in-built weak interface that directed crack propagation, our study produced an integrated model without preset weak interfaces, focusing on the dynamic evolution of the stress field that associates with crack initiation and propagation
The use of a pulsed laser light source as opposed to a continuous one enables the dynamic capture of clear isochromatic fringes because it has a frequency synchronized with that of the high-speed camera and a full width at half maximum (FWHM) on the order of nanoseconds

Summary

Introduction

Load-induced stress fields govern the deformation and fracture behaviour of solids. Knowledge of how those stress fields evolve yields valuable information that is used in a wide variety of practical applications[1,2,3,4,5,6,7,8,9,10,11,12,13]. Xia et al observed a shear crack propagating between two frictionally held or weakly boned identical pieces of brittle polyester resin under far-field asymmetric loading and found that the shear crack propagated faster than the shear wave speed[2,3,33] They investigated spontaneous mixed-mode fractures and self-similar crack growth behaviour[34,35,36]. Gomez et al.[37] captured the photoelastic fringe patterns of a Homalite-100 disc under dynamic tensile splitting and analysed the damage regions All of these studies offer straightforward approaches for capturing the dynamic-stress status in the fracture of a solid material yet lack quantitative visualisation of the continuous evolution of the stress field during crack rapid propagation. A valid quantitative visualisation of the instantaneous stress field that relates crack propagation in a solid material to its birefringence and elastic-brittle fracture properties is needed

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