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Najiba Hasan Hamad 《亚洲传热研究》2022,51(5):3794-3814
Classical Fourier's theory is well-known in continuum physics and thermal sciences. However, the primary drawback of this law is that it contradicts the principle of causality. To explore the thermal relaxation time characteristic, Cattaneo–Christov's theory is adopted thermally. In this regard, the features of magnetohydrodynamic (MHD) mixed convective flows of Casson fluids over an impermeable irregular sheet are revealed numerically. In addition, the resulting system of partial differential equations is altered via practical transformations into nonlinear ordinary differential equations. An advanced numerical algorithm is developed in this respect to get higher approximations for temperature and velocity fields, as well as their corresponding wall gradients. For validating our numerical code, the current outcomes are compared with the available literature results. Moreover, it is revealed that the velocity field is more prominent in the suction flow situation as compared with the injection flow case. It is also found that the Casson fluid is hastened in the case of lower yield stress. Larger values of thermal relaxation parameters create a lessening trend in the temperature distribution and its related boundary layer breadth. 相似文献
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The outcome of the cutting blasting in a one-step shaft excavation is heavily related to the cutting parameters used for parallel cutting method. In this study, the relationships between the cutting parameters (such as the hole spacing L and the empty hole diameter D) and damage zones were investigated by numerical simulation. A damage state index γ was introduced and used to characterize the crushing and crack damage zones through a user-defined subroutine. Two indices, i.e., η1 and η2 that can reflect the cutting performance, were also introduced. The simulation results indicate that an optimal value of L can be obtained so that the η1 and η2 can reach their optimal states for the best cutting performance. A larger D results in better cutting performance when the L value maintains its best. In addition, the influences of the loading rate and the in-situ stress on the cutting performance were investigated. It is found that an explosive with a high loading rate is suit for cutting blasting. The propagation direction and the length of the tensile cracks are affected by the direction and the magnitude of the maximum principal stress. 相似文献
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碳纤维复合材料薄壁圆筒为各向异性导热,其轴向导热系数是筒体温度场理论计算、成型工艺优化的重要参数。碳纤维复合材料圆筒由于较小的截面面积给筒体加热、热量有效传递带来了较大困难。本文以平板材料导热系数的稳态法测试国家标准为基础,基于傅里叶一维稳态导热原理,设计了一套用于薄壁圆筒轴向导热系数测试的装置,采用双试件对称加热、辐射换热防护及热对流环境控制等实现了热量沿筒体轴向的有效传导,利用该装置对导热系数已知的铝筒进行测试,验证了该装置设计的可行性,得到了碳纤维复合材料薄壁圆筒的轴向导热系数为(4.60±0.13) W/(m•K)。 相似文献
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根据用户要求,从空间布局和网络拓扑方面介绍了输入轴智能化生产线的建设过程,详述各环节的工作任务和动作机能,给出了主要零/部件的结构图样。生产线投用后,成效显著。对智能化制造商具有指导意义,对商用车用户具有借鉴意义。 相似文献
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针对目前大直径管道井施工存在的效率低、安全性和经济性差等问题,提出了反井钻机一次成井工艺,介绍了表土层开挖、导孔、扩孔、锚网喷支护、井筒管路安装等施工过程及施工要点。实践表明,反井钻机施工上庄管道井,井筒施工进度、质量、管路安装质量和工程费用优势明显,为大直径管道井施工方案选择提供有利参考。 相似文献
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Zequan YAO Chang FAN Zhao ZHANG Dinghua ZHANG Ming LUO 《Frontiers of Mechanical Engineering》2021,16(4):855
Machined surface roughness will affect parts’ service performance. Thus, predicting it in the machining is important to avoid rejects. Surface roughness will be affected by system position dependent vibration even under constant parameter with certain toolpath processing in the finishing. Aiming at surface roughness prediction in the machining process, this paper proposes a position-varying surface roughness prediction method based on compensated acceleration by using regression analysis. To reduce the stochastic error of measuring the machined surface profile height, the surface area is repeatedly measured three times, and Pauta criterion is adopted to eliminate abnormal points. The actual vibration state at any processing position is obtained through the single-point monitoring acceleration compensation model. Seven acceleration features are extracted, and valley, which has the highest R-square proving the effectiveness of the filtering features, is selected as the input of the prediction model by mutual information coefficients. Finally, by comparing the measured and predicted surface roughness curves, they have the same trends, with the average error of 16.28% and the minimum error of 0.16%. Moreover, the prediction curve matches and agrees well with the actual surface state, which verifies the accuracy and reliability of the model. 相似文献
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GH4169高温合金的薄壁钻孔与厚壁钻孔相比有特殊性,运用ABAQUS软件进行钻削GH4169高温合金薄壁件的仿真,研究钻削加工过程中钻削参数和工件厚度对钻削力的影响规律及变化特征,分析应力的分布规律。结果表明:钻削初期,横刃的挤压和主切削刃切削长度的增加使钻削力和扭矩增大;稳定钻削阶段,横刃切出后,主切削刃切削长度不变切削直径增加,钻削力和扭矩稳定增加;钻削后期,副切削刃参与切削,主切削刃切削长度减小,轴向钻削力和扭矩减小,但副刃与孔壁的挤压摩擦,曲线波动较大;钻削速度、进给量及工件厚度的增加都会导致轴向钻削力和扭矩的增加;钻削时的最大应力分布在横刃和主切削刃与工件的接触部位。 相似文献