摘要
对于三点弯曲U形切槽梁二等分线上的张开应力,如果用Creager和Paris的经典近似公式计算,则其适用范围很小;而用我们修正的公式计算,其适用范围几乎函盖U形切槽二等分线上整个拉伸区。由张开应力在U形切槽二等分线断裂过程区长度上积分,然后除以该长度得到平均张开应力;当其达到临界值时就得到包含拉伸强度和断裂韧度两个材料参数的平均应力破坏准则;利用这一准则提出用三点弯曲U形切槽梁同时测定这两个材料参数的新方法。因此,只要在实验时,制作一系列切槽深度相等而根部曲率半径不同的待测准脆性材料的U形切槽梁,用三点弯曲加载并分别测得其临界荷载,在已知应力集中系数的情况下,应用平均应力破坏准则就得到一超定方程组,再用恰当的数值方法便可解出拉伸强度和断裂韧度两个未知数。
The classic approximate formula proposed by Creager and Paris is generally used to calculate the opening stress of three-point bending U-notched beams along the bisector, but the scope of application is very limited. The modified formula proposed in this paper widens its application scope and can be applied to almost the whole tensile region of the ligament along the U-notch bisector. Integrating the opening stress along the U-notch bisector over the fracture process zone length and dividing the integral by the length, the average opening stress is obtained. Once it reaches the critical value, the average stress failure criterion with two material parameters, namely tensile strength and fracture toughness, is derived. Based on this criterion, a new method of concurrently measuring the two material parameters of quasi-brittle materials using three-point bending U-notched beams is proposed. A series of experiments are carried out for U-notched beams with same notch depth but different root radii, and critical loads in three-point bending are obtained. With the derived stress concentration factors, the average stress failure criterion is used to generate a series of over-determined equations, where the tensile strength and fracture toughness as two unknowns can be solved readily with a proper numerical method.
出处
《工程力学》
EI
CSCD
北大核心
2009年第9期244-250,共7页
Engineering Mechanics
基金
国家自然科学基金项目(10472075)
高校博士学科点专项基金项目(200806100042)
关键词
准脆性材料
拉伸强度
断裂韧度
三点弯曲U形切槽梁
近似应力公式
平均应力破坏准则
quasi-brittle materials
tensile strength
fracture toughness
three-point bending U-notched beam
approximate stress formula
average stress failure criterion
