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测量钢管屈服应力的目的是为了评估钢管对内部流体压力的抵抗能力。遗憾的是,不可能在环向取得一段直的试样,因此在进行试验之前,必须将钢管压扁。当前研究中,对不同材料以拉伸-压缩模式进行试验以便为随动硬化模型提供数据。以此试验数据为基础,建立一个模型,并将一些材料行为特征(屈服点伸长率的存在,应变硬化等)和工艺路线(直缝或螺旋缝焊接,扩径机,水压)等均考虑在内。钢管生产也在不同工艺段采样(母材、矫平后、成型后及水压后)。试验程序包括拉伸试验和环胀试验,结果显示该模型所给出的预测值与试验结果有良好对应。该模型还推出一些试验事实,例如屈服点伸长率在母材的存在及其在扁平管试样的不存在。最后,该模型与工业生产数据库相比,含有不同的钢级(从B级到X80级)和不同壁厚直径(壁厚/外径)比的数据值。该数据库所预测的钢卷和钢管的屈服应力差为20 MPa。
The purpose of measuring the yield stress of a steel tube is to evaluate the resistance of the steel tube against internal fluid pressure. Unfortunately, it is not possible to obtain a straight sample in the circumferential direction, so the pipe must be squashed prior to testing. In the current study, different materials were tested in tension-compression mode to provide data for follow-up hardening models. Based on this test data, a model was established and some material behavior characteristics (the existence of yield point elongation, strain hardening, etc.) and the process route (straight seam or spiral seam welding, expanding machine, water pressure) within consideration. Pipe production is also sampling in different sections (base metal, leveling, forming and water pressure). The test procedure includes the tensile test and the inflation test. The results show that the predicted value given by the model is in good agreement with the test result. The model also introduces a number of experimental facts, such as the presence of the yield point elongation in the parent metal and its absence in flat-tube samples. Finally, the model contains data values for different steel grades (from grade B to grade X80) and different wall thicknesses (wall thicknesses / outer diameters) compared to the industrial production database. The predicted difference of yield stress between the coil and the steel pipe of this database is 20 MPa.