特殊螺纹接头各向异性试验载荷包络线的计算

Calculation method of the premium connection anisotropic test load envelope

在石油套管特殊扣接头全尺寸评价试验中,对于材料性能,通常假设油井管材料是各向同性的,因此可以应用Mises等效应力公式计算试验载荷。但对于冷加工的耐蚀合金(CRA)材料,通常表现出各向异性,传统的计算方法存在着局限性。在新版的API 5C5-2017油套管接头评价试验标准中,已经认识到这一问题。在材料性能部分,提出了材料横向及压缩性能的试验内容,并指出试验结果可用于计算接头试验载荷包络线。本文通过力学性能试验进行了高合金材料各向异性的性能研究,并利用Hill各向异性屈服准则,计算出各向异性材料接头评价试验载荷包络线。试验结果表明,CRA材料表现出明显的各向异性,在进行特殊扣接头全尺寸评价试验时,可利用Hill公式计算试验载荷。

In the full-scale evaluation test of OCTG premium connection,it is usually assumed that the material of oil well pipes have isotropic properties,therefore,the Mises equivalent stress formula can be used to calculate the test load.However,for cold processed corrosion resistant alloy(CRA)materials,they usually show anisotropy,the traditional calculation method has its limitations.This problem has been recognized in the new edition of API 5C5-2017 test specification for casing and tubing connections.In the section of material properties,the test contents of transverse and compressive properties of materials are presented,and it is pointed out that the test results can be used to calculate the test load envelope.In this paper,the anisotropic properties of high alloy materials were studied by the mechanical properties test,and by using the Hill anisotropic yield criterion,the connection evaluation TLE(test load envelope)of the anisotropic material is calculated.The test results show that the CRA material shows obvious anisotropy,and the Hill formula can be used to calculate the test load in the full-scale evaluation test of premium connection.