The deformation of porous sintered materials

Summary It was established that iron-base sintered porous materials belong to the category of incompletely elastic media. For this reason, the principal problems in the mechanics of porous sintered materials may be satisfactorily solved with the aid of the mathematical devices relating to the mechanics of materials undergoing deformation in time.     

Strength of porous sintered sheet materials

Conclusions The strength of porous sintered sheet materials can be evaluated by the formaulas of Bal'shin, Ryshkevich, and Shcherban'. We determined the values of the constants in these formulas for sheets of powdered strainless steel of joint reduction, calcium hydride titanium, nickel, and Nichrome.In technological tests the largest number of reversed bendings is sustained by porous sheets rolled from powders of fine fractions. Differences in the plasticity of porous sheets from powdered stainless steel and Nichrome manifest themselves with bending radii of 2 and 5 mm.Translated from Poroshkovaya Metallurgiya, No. 2(302), pp. 92–96, February, 1988.     

The motion of gases and liquids in porous sintered materials

Summary The results are presented of an experimental study carried out with the object of determining the limits of applicability of the linear law of filtration — Darcy's law — for porous sintered materials.     

Cold extrusion forging of sintered porous materials

Conclusions Experiments have confirmed the validity of an arbitrary division of the back extrusion process of a porous blank into two consecutive stages: I) densification of porous material under the ram face to some and density and II) flow (back extrusion proper) of the densified material into an annular gap. During the deformation of blanks of starting densities equal to or greater than their threshold values the extrusion process, as in the case of incompressible (bulk) materials, takes place in a single stage — the flow stage. In cases where ₀ < _t the maximum densification pressure of a porous material and the extrusion pressure, which is equal to it, are virtually independent of the starting blank density; the parameter determining these pressures is the threshold density, which depends on the magnitude of transverse strain. Optimum power and force conditions prevail when blanks of starting density equal to the threshold density are used. In the forging of iron powder blanks of this density the extrusion pressure is 20% less than with bulk St. 10 steel. Analytical expressions have been derived enabling the power and force parameters — pressure and work — in each stage of the extrusion forging process of porous sintered materials to be determined.Translated from Poroshkovaya Metallurgiya, No. 11(215), pp. 28–34, November, 1980.     

Operating performance of sintered porous materials in a hot steam atmosphere

Conclusions It is suggested that the quality of SHT and the performance of SHT presses can be improved by replacing the standard three- or four-layer system of perforated plates and stretch covers fitted to the upper pads of ironing presses by a porous sintered plate with a rough working face. An investigation of the performance of porous metals in the SHT of articles of clothing revealed that sintered specimens of 50% porosity possess the required steam permeability. The roughness of the working surface should be varied depending on the fleeciness of the cloth to be pressed. The best results in SHT tests were obtained with porous titanium produced from mixed powder fractions with particles ranging from 0.3 to 1.0 mm in size.Translated from Poroshkovaya Metallurgiya, No. 11 (119), pp. 102–106, November, 1972.     

Elastoplastic deformation of sintered porous materials in forming processes. I. Theory of elastoplastic deformation of porous materials

Translated from Poroshkovaya Metallurgiya, No. 4, pp. 1.5, April, 1992.     

Procedure of determining the true compression strength of porous sintered materials

Conclusions The procedure proposed permits of eliminating the effect of contact friction in the determination of the true compressive strength of porous materials.Data characterizing the true compressive strength of porous materials as a function of the porosity have been obtained by means of the procedure reported.     

烧结镍基高温合金丝网多孔材料的抗氧化性能研究

采用静态增重法,测试了两种不同尺寸的烧结镍基高温合金丝网多孔材料样品及致密单丝样品在900℃下的氧化动力学曲线与氧化速率;采用9410型全自动压汞仪测试多孔小样品的表面积,同时通过透气系数计算其表面积,并据此对多孔小样品的氧化速率进行修正;用SEM、EDS及XRD等手段观察分析多孔样品氧化100 h后的显微形貌与氧化物的组成情况。结果表明:经过100 h氧化实验,大、小多孔样品的氧化速率为单丝样品的7倍左右;多孔小样品修正后的氧化速率远远小于修正前的氧化速率,也小于单丝样品的氧化速率;多孔样品的表面氧化物呈球形,分布较为均匀,其组成主要为Ni Cr_2O_4。     

The mechanical properties of sintered materials. I. The strength properties of sintered materials

Translated from Poroshkovaya Metallurgiya, No. 1(337), pp. 34–45, January, 1991.