The effect of yield-to-tensile strength ratio(Y/T) on failure pressure of X70 pipeline without and with corrosion defects was investigated.The stress-strain response of materials was characterized by a power-law harde...The effect of yield-to-tensile strength ratio(Y/T) on failure pressure of X70 pipeline without and with corrosion defects was investigated.The stress-strain response of materials was characterized by a power-law hardening curve.Two formulas to estimate the strain hardening exponent n for a special Y/T were obtained by least squared regression method and the influence of Y/T on n was analyzed.As an application of n-Y/T expression,the analytical solutions of burst pressure for X70 pipeline without and with corrosion defects were also obtained.The results indicate that the burst pressure of defect-free X70 pipe without corrosion defects is a function of the Y/T,pipe geometry t0/D0 and engineering tensile strength,and increases as Y/T or t0/D0 increases; whilst the burst pressure of corroded X70 pipe decreases with the increase of defect depths,d/t.Comparisons indicate that the present analytical solutions closely match available experimental and numerical data.展开更多
The effect of the low temperature treatment at -78 ℃ and -196 ℃ on the microstructure and properties of 18%SiC w/6061(volume fraction) Al alloy composites of as squeeze casting were studied. The results show that, a...The effect of the low temperature treatment at -78 ℃ and -196 ℃ on the microstructure and properties of 18%SiC w/6061(volume fraction) Al alloy composites of as squeeze casting were studied. The results show that, after the low temperature treatment, the dislocation density in matrix increases, and the residual stress of the matrix decreases, as well as the tensile yield strength of the composites improves. The high residual stress exists in the matrix of the composites of as original squeeze casting. The mismatch degree between the matrix and SiC w phases increases during the low temperature treatment. The matrix undergoes the tensile plastic deformation during the cooling procedure. On the contrary, the matrix encountered an elastic unloading procedure during the heating up process from low temperature to room temperature. The increase of dislocation density and the decrease of residual stress in the matrix are the main reason of the improvement for tensile yield strength of the composites.展开更多
In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica ...In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica were separately selected from 10 different natural forest zones while two logs were obtained from each tree. The logs were debarked and steamed in a vat prior to rotary peeling and slicing for veneer production. The optimum steam temperature was determined by considering different temperatures: 50℃, 60℃, 70℃, 80℃ and 90℃ for 24 h. Thereafter, optimum steam time was determined at the optimum temperature by considering durations of 24, 48, 72 and 96 h. The average taper of 0.75 mm per 1.0 m length was recorded for B. nigerica, indicating that the logs were reasonably cylindrical; thereby its logs are good for the production of veneer. The yield ranged from 44% to 61% with an average of 52% of the log input. The tensile strength of the veneer was tested perpendicular to grain and both peeled and sliced veneers had the highest tensile strength between 70℃ and 90℃, suggesting that softening of wood polymers, especially lignin, is between 70℃ and 90℃. The optimum temperature and time for veneer production are 70℃ and 48 h, respectively. Commercial production of veneer from B. nigerica is feasible based on the yield and mechanical properties of the obtained veneer, thereby encouraging the expansion of the scope of its utilization.展开更多
The tensile and fracture behavior of DZ951 directionally solidified Ni-base superalloy was studied in the temperature range of 20-1 100℃. The fracture mode was examined by scanning electron microscopy. The results sh...The tensile and fracture behavior of DZ951 directionally solidified Ni-base superalloy was studied in the temperature range of 20-1 100℃. The fracture mode was examined by scanning electron microscopy. The results show the experimental temperature has no significant effect on the tensile strengths, which are greater than 1 000 MPa from room temperature to 800℃. The yield strength reaches its maximum (970 MPa) at 800℃. When the experimental temperature is higher than 800℃, the tensile and yield strengths decrease evidently and the ductility increases remarkably. The fractograph of fracture surface for the tensile specimen at room temperature shows a dimple-ductile fracture mode. The fractograph from 600 to 800℃shows a slide fracture mode. The fractograph from 900 to 1 100℃exhibits a creep rupture mode with uneven deformation.展开更多
Due to the large unexplored compositional space,long development cycle,and high cost of traditional trial-anderror experiments,designing high strength aluminum-lithium alloys is a great challenge.This work establishes...Due to the large unexplored compositional space,long development cycle,and high cost of traditional trial-anderror experiments,designing high strength aluminum-lithium alloys is a great challenge.This work establishes a performance-oriented machine learning design strategy for aluminum-lithium alloys to simplify and shorten the development cycle.The calculation results indicate that radial basis function(RBF)neural networks exhibit better predictive ability than back propagation(BP)neural networks.The RBF neural network predicted tensile and yield strengths with determination coefficients of 0.90 and 0.96,root mean square errors of 30.68 and 25.30,and mean absolute errors of 28.15 and 19.08,respectively.In the validation experiment,the comparison between experimental data and predicted data demonstrated the robustness of the two neural network models.The tensile and yield strengths of Al-2Li-1Cu-3Mg-0.2Zr(wt.%)alloy are 17.8 and 3.5 MPa higher than those of the Al-1Li4.5Cu-0.2Zr(wt.%)alloy,which has the best overall performance,respectively.It demonstrates the reliability of the neural network model in designing high strength aluminum-lithium alloys,which provides a way to improve research and development efficiency.展开更多
针对大厚径比HFW海洋管制管过程中纵向屈强比上升的问题,研究了化学成分、冷却工艺对X65MO管线钢组织和性能的影响。结果表明,增加C元素含量或去除V元素有利于降低材料预拉伸后的纵向屈强比;试验材料在高温下卷取,其显微组织为铁素体+...针对大厚径比HFW海洋管制管过程中纵向屈强比上升的问题,研究了化学成分、冷却工艺对X65MO管线钢组织和性能的影响。结果表明,增加C元素含量或去除V元素有利于降低材料预拉伸后的纵向屈强比;试验材料在高温下卷取,其显微组织为铁素体+珠光体,轧态纵向拉伸曲线具有较长的屈服平台,预拉伸后具有最低的屈强比和最高的均匀延伸率;随着卷取温度降低,晶粒更加细小,贝氏体组织增加,预拉伸后的纵向屈强比上升幅度较大,而在相同卷取温度下,降低冷却速度有利于降低预拉伸后的纵向屈强比。根据研究结果制定了卷板工艺,试制了X65MO钢级Φ323.9 mm×14.3 mm HFW海管,管材横纵向屈强比等拉伸性能均满足规范要求。展开更多
基金Project(N110607002)supported by the Fundamental Research Funds for the Central Universities of ChinaProject(51074052)supported by the National Natural Science Foundation of China
文摘The effect of yield-to-tensile strength ratio(Y/T) on failure pressure of X70 pipeline without and with corrosion defects was investigated.The stress-strain response of materials was characterized by a power-law hardening curve.Two formulas to estimate the strain hardening exponent n for a special Y/T were obtained by least squared regression method and the influence of Y/T on n was analyzed.As an application of n-Y/T expression,the analytical solutions of burst pressure for X70 pipeline without and with corrosion defects were also obtained.The results indicate that the burst pressure of defect-free X70 pipe without corrosion defects is a function of the Y/T,pipe geometry t0/D0 and engineering tensile strength,and increases as Y/T or t0/D0 increases; whilst the burst pressure of corroded X70 pipe decreases with the increase of defect depths,d/t.Comparisons indicate that the present analytical solutions closely match available experimental and numerical data.
文摘The effect of the low temperature treatment at -78 ℃ and -196 ℃ on the microstructure and properties of 18%SiC w/6061(volume fraction) Al alloy composites of as squeeze casting were studied. The results show that, after the low temperature treatment, the dislocation density in matrix increases, and the residual stress of the matrix decreases, as well as the tensile yield strength of the composites improves. The high residual stress exists in the matrix of the composites of as original squeeze casting. The mismatch degree between the matrix and SiC w phases increases during the low temperature treatment. The matrix undergoes the tensile plastic deformation during the cooling procedure. On the contrary, the matrix encountered an elastic unloading procedure during the heating up process from low temperature to room temperature. The increase of dislocation density and the decrease of residual stress in the matrix are the main reason of the improvement for tensile yield strength of the composites.
文摘In an effort to find suitable wood from natural forest to meet the demand for veneer products, the yield and tensile strength of veneers produced from Brachystegia nigerica were investigated. Two trees of B. nigerica were separately selected from 10 different natural forest zones while two logs were obtained from each tree. The logs were debarked and steamed in a vat prior to rotary peeling and slicing for veneer production. The optimum steam temperature was determined by considering different temperatures: 50℃, 60℃, 70℃, 80℃ and 90℃ for 24 h. Thereafter, optimum steam time was determined at the optimum temperature by considering durations of 24, 48, 72 and 96 h. The average taper of 0.75 mm per 1.0 m length was recorded for B. nigerica, indicating that the logs were reasonably cylindrical; thereby its logs are good for the production of veneer. The yield ranged from 44% to 61% with an average of 52% of the log input. The tensile strength of the veneer was tested perpendicular to grain and both peeled and sliced veneers had the highest tensile strength between 70℃ and 90℃, suggesting that softening of wood polymers, especially lignin, is between 70℃ and 90℃. The optimum temperature and time for veneer production are 70℃ and 48 h, respectively. Commercial production of veneer from B. nigerica is feasible based on the yield and mechanical properties of the obtained veneer, thereby encouraging the expansion of the scope of its utilization.
文摘The tensile and fracture behavior of DZ951 directionally solidified Ni-base superalloy was studied in the temperature range of 20-1 100℃. The fracture mode was examined by scanning electron microscopy. The results show the experimental temperature has no significant effect on the tensile strengths, which are greater than 1 000 MPa from room temperature to 800℃. The yield strength reaches its maximum (970 MPa) at 800℃. When the experimental temperature is higher than 800℃, the tensile and yield strengths decrease evidently and the ductility increases remarkably. The fractograph of fracture surface for the tensile specimen at room temperature shows a dimple-ductile fracture mode. The fractograph from 600 to 800℃shows a slide fracture mode. The fractograph from 900 to 1 100℃exhibits a creep rupture mode with uneven deformation.
基金supported by the National Natural Science Foundation of China(Nos.52074246,52275390,52205429,52201146)National Defense Basic Scientific Research Program of China(JCKY2020408B002)Key Research and Development Program of Shanxi Province(202102050201011,202202050201014).
文摘Due to the large unexplored compositional space,long development cycle,and high cost of traditional trial-anderror experiments,designing high strength aluminum-lithium alloys is a great challenge.This work establishes a performance-oriented machine learning design strategy for aluminum-lithium alloys to simplify and shorten the development cycle.The calculation results indicate that radial basis function(RBF)neural networks exhibit better predictive ability than back propagation(BP)neural networks.The RBF neural network predicted tensile and yield strengths with determination coefficients of 0.90 and 0.96,root mean square errors of 30.68 and 25.30,and mean absolute errors of 28.15 and 19.08,respectively.In the validation experiment,the comparison between experimental data and predicted data demonstrated the robustness of the two neural network models.The tensile and yield strengths of Al-2Li-1Cu-3Mg-0.2Zr(wt.%)alloy are 17.8 and 3.5 MPa higher than those of the Al-1Li4.5Cu-0.2Zr(wt.%)alloy,which has the best overall performance,respectively.It demonstrates the reliability of the neural network model in designing high strength aluminum-lithium alloys,which provides a way to improve research and development efficiency.
文摘针对大厚径比HFW海洋管制管过程中纵向屈强比上升的问题,研究了化学成分、冷却工艺对X65MO管线钢组织和性能的影响。结果表明,增加C元素含量或去除V元素有利于降低材料预拉伸后的纵向屈强比;试验材料在高温下卷取,其显微组织为铁素体+珠光体,轧态纵向拉伸曲线具有较长的屈服平台,预拉伸后具有最低的屈强比和最高的均匀延伸率;随着卷取温度降低,晶粒更加细小,贝氏体组织增加,预拉伸后的纵向屈强比上升幅度较大,而在相同卷取温度下,降低冷却速度有利于降低预拉伸后的纵向屈强比。根据研究结果制定了卷板工艺,试制了X65MO钢级Φ323.9 mm×14.3 mm HFW海管,管材横纵向屈强比等拉伸性能均满足规范要求。