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In technology, a common helical surface is a right closed helicoid (auger). It is formed by a helical movement of a horizontal segment, provided that the axis of the auger crosses at one of its ends. The formation of the surface of an open helicoid is similar but the segment must intersect the axis and be located at a constant distance from it. It is known from differential geometry that the helical surface can be transformed by bending to the surface of rotation. This fact is taken as the basis for calculating the geometric shape of a flat workpiece. The surface of the open helicoid is non-disjointed, so the shape of the workpiece must be found in such a way as to minimize plastic deformations during surface formation. Parametric equations of continuous flexion of the turn of an open helicoid into the section of a single-cavity hyperboloid of rotation have been derived. Continuous bending can be represented as a gradual deformation of the turn while reducing its step. The meridian of hyperboloid rotation is the corresponding area of hyperbola. The hyperboloid section is proposed to be approximated by the surface of the truncated cone. This approximation will be more accurate in the area of the hyperbole where it asymptotically approaches the segment of the right line. After selecting a cone, it becomes possible to determine its size and build its exact sweep since the cone is a unfolding surface. The sweep is constructed in the form of a flat ring with a cut sector and will be the desired flat workpiece to form a turn of the auger from it. Most accurately, the surface of the turn of the open helicoid can be made by stamping the workpiece of the resulting form. For small-scale production of the helical surface of an open helicoid, it is advisable to weld flat rings together and, during installation, stretch along the shaft while twisting around its axis. The accuracy of the obtained surface will depend on the accuracy of the approximation of the hyperboloid section of rotation with a truncated cone, which is the topic of this work. [ABSTRACT FROM AUTHOR]

In this study, we investigated the macro and micro mechanisms of bamboo bending failure, and a new method to unfasten bamboo fiber by continuous bends and large deformations is put forward. The method could effectively maintain the fiber structure integrity without damage. Bamboo strip with load deformation was considered a continuous beam, and the bending moment and the matrix cracking of the bamboo were analyzed on the basis of elastically plastic theory. The mechanical model to unfasten the bamboo fiber under continuous bending was established using the principle of virtual work, while the loading conditions were obtained. The arithmetic expressions for the loading roller diameter and distance, as the main parameters, were obtained analyzing bamboo splitting under different strain conditions. The fiber splitting test further verifies our method and models, which provide a new idea and way for bamboo fiber splitting by mechanical method. [ABSTRACT FROM AUTHOR]

Abstract The effect of rolling speeds varying from 0.1 to 0.4 m/s on texture modifications and mechanical properties of AZ31 magnesium alloy sheets processed by a combination of equal channel angular rolling and continuous bending (ECAR+CB) at high temperature (550 °C) was investigated in this work. After annealing, the processed AZ31 sheets exhibit rolling direction (RD)-split texture with increasing rolling speeds. The RD-split texture component is non-basal texture and named as "Zn" texture. Due to the "Zn" texture, the Erichsen values remarkably increase to 7.4 mm at room temperature. This work suggests that ECAR+CB processing is a promising technology for texture modification in Mg alloy sheets regarding improving room formability. Highlights • RD-split texture (Zn-texture) is produced in AZ31 sheet via equal channel angular rolling and continuous bending (ECAR+CB). • Due to the "Zn" texture, the Erichsen values remarkably increase to 7.4 mm. • ECAR+CB will be a promising technology for texture modification in Mg alloys sheets. [ABSTRACT FROM AUTHOR]

This work aimed to alter the texture components and enhance the stretch formability of rolled AZ31 sheets by developing the rolling technology. In this study, a continuous bending channel was introduced into an equal channel angular rolling apparatus and a new rolling technology was successfully developed. Microstructure evolutions during hot-rolling, equal channel angular rolling and subsequent continuous bending were investigated. Results showed that hot-rolling generated a strong basal texture component. Single pass equal channel angular rolling cannot eliminate the basal texture component, while can greatly weaken basal texture intensity. After continuous bending, basal texture component was almost eliminated. Meanwhile, a strong c-axis//RD texture component and a weak double-peak texture component with symmetrical splitting of the {0002} basal texture were formed. After recrystallization annealing, symmetrical double-peak texture whose {0002} pole peak located at about 40° from normal direction towards the rolling direction was enhanced with the disappearance of c-axis//RD texture. The AZ31 sheets with double-peak texture exhibited excellent stretch formability at room temperature (with an Erichsen value of 7.4 mm). Finally, the relevant mechanisms were discussed. [ABSTRACT FROM AUTHOR]

In the present study, we developed an integrated process that combined high-temperature rolling and continuous bending as a single processing step, i.e., the HTR-CB process, and the process was carried out on Mg-3Al-1Zn magnesium alloy sheet in order to improve its ductility at room temperature. The microstructure, texture and mechanical property of the HTR-CB sample were investigated. The results show that the HTR-CB sample after annealing exhibits a high Erichsen value of 6.9, which is more than 1.5 times larger than that (4.6) in the HTR sheet, mainly due to the formation of non-basal textures with double peaks titling at the range of ± 30°~ ± 38° from the normal direction towards the rolling direction. The main reasons for the texture modifications during the HTR-CB process and annealing are discussed.

The effects of V-bending process, continuous bending process and combination process on the microstructure and mechanical properties and formability of an AZ31 magnesium alloy sheet were investigated. The experimental results showed that no twins were found in the microstructure of all samples after processes due to the fine grain. The V-bending and continuous bending processes were proved to be an effective approach to modify the mechanical properties and formability. While the samples after the combination process exhibited better mechanical properties and formability than the single processed sample. The yield strength significantly decreased with the value of 100 MPa and the fracture elongation enhanced to 18.3% at room temperature. The Erichsen value was 5.0 mm which was significantly increased by 117% compared with as-received sample. The superior formability of combination processed samples was mainly attributed to the smaller r -value and n -value. [ABSTRACT FROM AUTHOR]

In the present study, we developed an integrated process that combined high-temperature rolling and continuous bending as a single processing step, i.e., the HTR-CB process, and the process was carried out on Mg-3Al-1Zn magnesium alloy sheet in order to improve its ductility at room temperature. The microstructure, texture and mechanical property of the HTR-CB sample were investigated. The results show that the HTR-CB sample after annealing exhibits a high Erichsen value of 6.9, which is more than 1.5 times larger than that (4.6) in the HTR sheet, mainly due to the formation of non-basal textures with double peaks titling at the range of ± 30°~ ± 38° from the normal direction towards the rolling direction. The main reasons for the texture modifications during the HTR-CB process and annealing are discussed. [ABSTRACT FROM AUTHOR]