Tao Wei, Sijin Zhao, Zongzhan Gao, Ke Zhang, Wenxuan Gou and Yangfan Dang
Fatigue and creep are the key factors for the failure of polymethyl methacrylate (PMMA) in the engineering structure, so a great of quantity attention is focused on the life…
Abstract
Purpose
Fatigue and creep are the key factors for the failure of polymethyl methacrylate (PMMA) in the engineering structure, so a great of quantity attention is focused on the life prediction under the creep and fatigue conditions. This paper aims to mainly summarize the traditional life assessment method (S–N curve), life assessment method based on crazing density and life assessment method based on transmittance. S–N curve and classical creep curve are introduced on the traditional life assessment method; the variation of the craze density with the logarithm of cyclic numbers is given in different fatigue load. A linear relationship is obtained, and a higher stress leads to a higher slope, suggesting a faster growth of craze. Furthermore, a craze density model is purposed to describe this relationship; the variation of craze density with the time at different creep load is given. The craze density has two obvious stages. At the first stage, craze density ranged from approximately 0.02 to 0.17, and a linear relationship is obtained. In the following stage, a nonlinear relationship appears till specimen rupture, a new creep life model is proposed to depict two stages. The relationship between transmission and time under creep load is shown. With increasing of time, the transmittance shows a nonlinear decrease. Through polynomial nonlinear fitting, a relationship between the transmittance and residual life can be obtained. To provide reference for the life assessment of transparent materials, the paper compares three life assessment methods of PMMA.
Design/methodology/approach
This paper uses the traditional life assessment method (S–N curve), life assessment method based on crazing density, life assessment method based on transmittance.
Findings
The variation of the craze density with the logarithm of cyclic numbers is given in different fatigue loads. A linear relationship is obtained, and a higher stress leads to a higher slope, suggesting a faster growth of craze. Furthermore, a craze density model is proposed to describe this relationship, and the variation of craze density with the time at different creep loads is given. The craze density has two obvious stages. The relationship between transmission and time under creep load is shown. With increasing of time, the transmittance shows a nonlinear decrease. Through polynomial nonlinear fitting, a relationship between the transmittance and residual life can be obtained.
Originality/value
Fatigue and creep are the key factors for the failure of PMMA in the engineering structure, so a great of quantity attention is focused on the life prediction under the conditions of creep and fatigue. This paper mainly summarizes traditional life assessment method (S–N curve), life assessment method based on crazing density and life assessment method based on transmittance.
Details
Keywords
Zongzhan Gao, Qinghai Li and Yi Wang
A series of creep experiments were carried out to study a new criterion for creep residual life assessment of PMMA (MDYB-10) with various stresses level at room temperature. A…
Abstract
Purpose
A series of creep experiments were carried out to study a new criterion for creep residual life assessment of PMMA (MDYB-10) with various stresses level at room temperature. A macroscopical creep life model based on abundant experiments results was researched first. The model included three phases which are described by the Chen theory, Norton formula and exponential expression, respectively. The paper aims to discuss these issues.
Design/methodology/approach
During the creep experiments, the simple optical testing instrument was used to observe the crazing initiation and quantify the crazing damage density in the specimens.
Findings
It was shown that the initiation time of crazing damage depended on the stress level, and the crazing damage density increased non-linearly with experiment time. The crazing initiation time equation and damage density equations were expressed.
Originality/value
Comprehensive consideration of the creep life model and crazing density evolution equation, a new criterion for creep residual life assessment was introduced. The criterion could be applied to assess the residual life for MDYB-10 by measuring the crazing damage density.