四點彎曲試驗下砂岩之複合型斷裂韌度與其基本力學性質之研究

Sandstone Mixed-Mode Fracture Toughness under Four-Point Bending Test and Basic Mechanical Properties

10.30069/MM.201809_62(3).0004

張育源(Y. Y. Chang)；郭俊志(C. C. Kuo)；王建力(C. L. Wang)

砂岩 ； 四點彎曲 ； 試驗 ； 複合型斷 ； 裂韌度 ； Sandstones ； Four-Point bending test ； Mixed-mode fracture toughness

鑛冶：中國鑛冶工程學會會刊

62卷3期（2018 / 09 / 01）

36 - 40

繁體中文

本研究使用砂岩為試驗材料，將此材料製備成單裂縫矩型試體，以施加的跨距變化作為操作變因進行四點彎曲試驗並將不同跨距與破壞應力帶入推導公式，求得複合型破裂韌度。本研究發現不同跨距會產生不同K值的破壞。I-II型部分三種跨距會各別產生純I型、I-II複合型與純II型破壞。II-III型部分K_(II)值與K_(III)值均會依不同的跨距設計而有所變化。斷裂面粗糙度部分，I-II型部分隨著純I型、I-II複合型與純II型先下降後上升，II-III型部分的粗糙度與不同的跨距設計無明顯關聯。I-II型與II-III型兩者斷裂面上都帶有與施力方向相同的細微帶狀溝槽。

Single edge-cracked bending sandstone specimens under four-point bending configurations were used to measure the mixed-mode fracture toughness. Two different experimental setups of four-point bending tests for modes I-II and II-III were respectively carried out in this study. There were three loading conditions for measuring the mode I-II fracture toughness and three loading conditions for measuring the mode II-III fracture toughness. We adopted Wang et al. (1979) mathematical model for mode I-II fracture toughness and Tohgo et al. (1986) mathematical model for mode II-III fracture toughness. A series of experiments were conducted on these specimens to determine the mixed-mode fracture toughness, uniaxial compressive strength, dynamic Young's modulus, dynamic Poisson's ratio and surface roughness. Mixed-mode fracture toughness was correlated with other mechanical properties. For the cases of mode I-II testing, the loading conditions were chosen for three fracture modes: pure mode I, mode I-II, and pure mode II. It was observed that the surface roughness in pure mode II loading was higher than that in pure mode I loading. The surface roughness in mode I-II loading is lowest. For the cases of mode II-III testing, it was observed that the mode II fracture toughness was proportional to the mode III fracture toughness. The measured surface roughness in mode II-III testing apparently did not show any relevance in three loading conditions. Slight grooves oriented along the loading direction on the fracture surface were observed for both modes I-II and II-III tests.

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1. 郭俊志,張育源,石秉儒,王建力(2019)。以四點彎曲試驗量測不同溫度作用下砂岩複合型斷裂韌度之研究。中國土木水利工程學刊，31(7)，623-633。
2. 李權仁(2019)。以四點彎曲試驗決定I+II型斷裂韌度之有限元素數值模擬。鑛冶：中國鑛冶工程學會會刊，63(4)，20-37。