Extrusion of axi-symmetric bi-metallic tubes: some experiments using hollow billets and the application of a generalised slab method of analysis

A generalised slab method of analysis is developed for the extrusion of axi-symmetric bi-metallic tubes through profiled shaped dies and over profile shaped mandrels. It is applied to different combinations of die shapes and mandrels. An experimental investigation into forward extrusion of bi-metallic tubes made of cp aluminium and hc copper was also carried out and the resultant non-dimensionalised extrusion pressures, flow patterns and characteristic deformation modes observed are given and the results commented upon. The theoretical results of extrusion pressures obtained from the analysis are compared with the experimental as well as those of other authors. These show reasonably good agreement.     

Extrusion of axi-symmetric bi-metallic tubes from solid circular billets: application of a generalised upper bound analysis and some experiments

The generalised upper bound technique previously applied to the determination of working pressures in extrusion–piercing of solid billets (Chitkara NR, Aleem A. Int J Mech Sci 2001;43:1685–709.) to form hollow monometallic tubes is extended to analyse the problem of bi-metallic tube extrusions through profile shaped dies and mandrel combinations. Theoretical results of mean extrusion pressures obtained from the generalised upper bound analysis are compared with those obtained earlier by the generalised slab method of analysis (Chitkara NR, Aleem A. Int J Mech Sci 2001;43:2857–82.) and some experiments. A few salient observations made during the experimental investigations carried out into forward extrusion of bi-metallic tubes made of h.c. copper and c.p. aluminium are also given and the results commented upon.     

Axi-symmetric tube extrusion/piercing using die–mandrel combinations: some experiments and a generalised upper bound analysis

A generalised upper bound technique is applied to the solution of working pressures in extrusion–piercing of hollow tubes starting from either solid circular or initially hollow billets by using axi-symmetric die–mandrel combinations of different shapes. Characteristic deformation modes during processing of these tubes made of tellurium lead and commercially pure aluminium were studied experimentally and the results presented. Estimates of working pressures based on the generalised upper bound analysis are compared with the experimental and with those estimated earlier from the slab method of analysis given in Chitkara and Aleem (International Journal of Mechanical Sciences, submitted for publication). These show good co-relations with each other and with the experiments.     

Forging and heading of hollow spur gear forms: an analysis and some experiments

To analyse the process of incremental forging and heading of hollow spur gear forms from initially ring-type specimens, the two types of theoretical approaches followed were an adaptation of the upper bound technique, applied previously to the solution of solid spur gear form forging (Chitkara NR, Bhutta MA. International Journal of Mechanical Sciences 1996;38(8–9):891–916) and the modification of the slab method of analysis given earlier for the case of spline forging and adapting it to the tapered teeth representing the actual profile teeth of the spur gear with the pressure angle of 14 °, (Chitkara NR, Bhutta MA. International Journal of Mechanical Sciences 1996;38(8–9):871–89). In each case, the theoretical results estimated were compared with those obtained experimentally during quasi-static forging and heading of hollow spur gear forms using the model material, tellurium lead. The characteristic deformation modes and some salient observations made on working pressures are given and the results commented upon.     

Axi-symmetric tube extrusion through a smooth conical or cosine die and over a conical or ogival mandrel: numerical construction of axi-symmetric slip-line fields and associated velocity fields

The numerical method of construction of axi-symmetric slip-line fields and their associated velocity fields suggested earlier for rod extrusion (Chitkara NR, Butt MA. Axi-symmetric rod extrusion through smooth conical, cosine and lat-faced dies, International Journal of Mechanical Sciences, submitted) and tube extrusion (Chitkara NR, Butt MA. Axi-synnetric tube extrusion through a flat-faced circular die: International Journal of Mechanical Sciences, 1997;39(3);341–366) is employed to construct slip-line fields and their associated velocity fields for a few cases of forward tube extrusion through smooth, rigid conical and cosine dies and over a smooth rigid conical or ogival mandrel. The computographic plots of slip-line fields and associated velocity fields are given in the form of weighted and directed velocity vectors as are the normal pressure distribution on both the die and the mandrel surfaces. The values of the non-dimensionalised mean extrusion pressures, are compared in each case with a similar case of plane strin extrusion and the results commented upon.     

正交试验法在抽油机井管杆偏磨失效分析中的应用

采用正交试验法揭示了影响水驱抽油机井管杆偏磨的主要人为控制因素对检泵周期影响的规律性，从中找出各因素对检泵周期影响的主次关系，并确定出最优的工艺条件组合。运用方差分析理论处理试验结果，得出各因素对管杆偏磨井检泵周期影响的显著程度，从而发现最薄弱环节，为科学治理和有效控制管杆偏磨失效，降低水驱抽油机井检泵率提供合理依据。