Measurement and formulation of the deformation behavior of thermoplastic polyetherester elastomer using biaxial stress tests

2020 Fiscal Year Final Research Report

• Project/Area Number: 18H01744
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Basic Section 26050:Material processing and microstructure control-related
• Research Institution: Tokyo University of Agriculture and Technology
• Principal Investigator: Kuwabara Toshihiko 東京農工大学, 工学(系)研究科(研究院), 卓越教授 (60195609)
• Project Period (FY): 2018-04-01 – 2021-03-31
• Keywords: ポリエチレン / 二軸応力 / 材料試験 / 異方性 / 等仕事面 / 破断限界

Outline of Final Research Achievements

A material testing apparatus for measuring the biaxial deformation behavior of a polymer tube is developed to quantitatively evaluate a deformation behavior of polymeric materials. The testing apparatus can apply an axial force and internal pressure to a tubular specimen. Polyethylene tubes with an outer diameter of 17 mm and a thickness of 2 mm are used as a test specimen, and are subjected to linear stress paths with stress ratios of σφ;:σθ=1:0, 4:1, 2:1, 4:3, 1:1, 3:4, 1:2, 1:4, and 0:1, where σφ and σθ are the axial and circumferential stress components applied to the center of the bulging specimen, respectively. Biaxial stress-strain curves are successfully measured for every linear stress path at a nearly constant logarithmic strain rate of 1×10-3 s-1. The maximum equivalent strain is achieved up to 0.71 for a specimen with a stress path of σφ:σθ=2:1. The contours of equal work plotted in the principal stress space show significant anisotropy of the test material.

Free Research Field

塑性力学

Academic Significance and Societal Importance of the Research Achievements

地震国である日本では，樹脂円管の耐震性や可撓性に関する研究は多くあるが，単軸引張/圧縮応力試験のように単純応力状態における試験に限定されている．一方，土中に埋設されたＰＥ管が地震時に受ける応力状態は軸力と同時に内圧も受け，多軸応力状態であるが、そのような多軸応力状態における変形挙動を数値シミュレーションする場合に必要となる材料モデル構築に関する研究は極めて少ない．樹脂円管の安全性評価指標の高度化のためには，二軸応力試験方法の確立と高精度な材料モデルの構築が急務であり、本研究成果はそれらの基礎研究として役に立つ。