The forming region and mechanical properties of CaO-Al2O3-SiO2 system

Glass system with compositions of 93.9% (xCaO-yAl₂O₃-zSiO₂)−5% MgO-1% B₂O₃−0.1% Fe₂O₃ has been prepared by a conventional melt-quenching technique, and the glass forming region and the mechanical properties of the derived glasses were investigated. The approximate glass forming region was found to be x = 10～35%, y = 10～35% and z = 50～80%, while the rest of the area was crystallization zone or crack zone. As x = 10%, y = 25% and z = 65% (Sample 13), the investigated glass possesses the optimum volume density, bending strength, compression strength and modulus, which are 2.572 g/cm³, 74.05 MPa, 312.84 MPa and 163.96 GPa, respectively. Compared to sample 13, samples with different compositions have reduced the volume density, lowered the Raman intensity and improved the optical band gap. For the mechanical properties, with decreasing the contents of SiO₂, the bending strength firstly increases, then decreases and finally shows a relatively small increasing trend. The dependence of compression strength and compression modulus on SiO₂ content shows a similar trend to the bending strength. Moreover, the optical band gap and Raman spectrum of the sample 13 indicate that the number of oxygen bonds in the bridge reach the maximum, which could further confirm a significantly improvement on the mechanical properties.     

Theoretical analysis and experimental study to support the development of a more valuable roll-bending process

A new roll-bending model is proposed which improves upon traditional roll-bending processes. The new forming model not only resolves some inadequacies of traditional roll-bending processes, but also allows more flexibility in the formation of large bending parts. The upper-bound and lower-bound methods are used to research the bending mechanisms of roll-bending processes and to provide some rules for the development of a new roll-bending process. Finite element modeling is also implemented for comparison with the upper-bound and lower bound results. Finally, a roll-bending experiment was carried out to attempt a real application, with the design of the experimental device based on the new roll-bending concept. All these efforts demonstrate that the new roll-bending model has potential for future use in industry.     

激光加热弯曲成型技术

板材激光加热弯曲成形是近年来提出的一种先进的零件成形方法。通过对金属板材激光加热弯曲成型的特点分析,探讨了激光加热弯曲成型的机理,同时对这一技术的发展现状作了归纳并对其发展进行了展望。     

锌合金蜗轮和铝青铜蜗轮弯曲强度和耐磨性研究

对锌基耐磨合金蜗轮和铝青铜蜗轮弯曲强度和耐磨性能进行了实验研究,结果得出,锌基合金的蜗轮较好。     

Machining stability in high-speed drilling—Part 1: Modeling vibration stability in bending

In this work, dynamic models for chatter in drilling are developed that deal with the transverse vibration due to bending, and the axial vibration due to torsion. In the first part, a dynamic model is developed to obtain the limit of stability for the bending vibration mode. The equations of motion are formulated based on a lumped representation of the drill, and the gyroscopic effect due to the rotation of the tool is included. It is shown that, including this gyroscopic effect has a profound effect on the resulting stability lobes, especially at very high speeds; it makes the lobes wider but at the same time lowers the minimum stability boundary. In the second part of this work, a time domain simulation model is developed that combines both bending and torsion modes. This model is verified [1] using experimental cutting tests.     

Experimental characterisation in sheet forming processes by using Vickers micro-hardness technique

In this paper, an experimental micro-hardness procedure is proposed to evaluate the evolution of HSLA steel behaviour during each sequence of sheet forming process. As micro-hardness technique offers a reliable inspection, it was retained here to follow the mechanical characteristic changes, which may happen during manufacturing progress. This contribution consists in characterisation of sheet material at different steps: virgin sheet, unreeled sheet, straightened sheet and bent sheet. Measurement performed on virgin HSLA steel showed that material is highly heterogeneous within the sheet thickness. The micro-hardness profiles examined after the bobbing-off step showed a high sensitivity of sheet behaviour to straightening operation that is widely adopted in steel working in order to make sheet sufficiently flat for forming. A level of hardening ratio between virgin material and straightened material has been clearly observed. Moreover, micro-hardness is investigated on bent parts at the fold zone for displaying the mechanical properties modifications under a large gradient deformation. In this way, hardening phenomenon and damage phenomenon, which are generally activated simultaneously for elastoplastic steel, are quantified accurately. Results compared into them gave a good idea about the interaction of process–material during manufacturing.     

高强度钢冲压回弹量对板料力学性能参数的灵敏度分析

回弹是板料冲压成形中影响冲压件质量的关键因素之一。本文采用正交试验方法,以典型高强钢DP钢U形件弯曲为例,对影响回弹的板料力学性能参数进行了灵敏度分析。考虑各参数按照相同百分比波动时的灵敏度分析结果表明：弹性模量对板料回弹量的影响最大,其次分别为硬化系数、初始屈服应力、硬化指数以及各向异性参数r0,而各向异性参数r45及r90对回弹量的影响可忽略。考虑各参数按照不同百兮比波动时的灵敏度分析结果表明：弹性模量对回弹量的影响最大,其次分别为硬化系数、硬化指数、初始屈服应力以及备向异性参数r0,而r45及r90对回弹量的影响则可忽略。所以,板料的力学性能参数中弹性模量对回弹的影响最明显,其次为硬化系数、硬化指数、初始屈服应力及各向异性参数r0,而r45及r90对回弹量几乎没有影响。     

The relationship between case depth and bending fatigue strength of gas carburized SAE 8620 steel

The fatigue performance of gas carburized SAE 8620 steel was evaluated as a function of case depth. To vary the case depths, different carburizing times were applied. The typical times were: 45 min, 3 and 5 h at the temperature of 940 °C. To cause failure in the rotating bending fatigue specimens, the applied load was chosen as the equivalent load at 10⁶ cycles for the material when is subjected to bending fatigue. The characterization of the specimens was carried out using X-ray diffraction technique for stress measurement and retained austenite and optical metallographic examination. The fractured surfaces were cleaned in an ultrasonic bath and examined using scanning electron microscope (SEM) equipped with EDX to evaluate the crack initiation and growth characteristics of the materials in the core and carburized case regions of specimens. The results showed that the fatigue limit was associated with the microstructure, the case depth, the distribution of retained austenite, the depth of the internal oxidation and the compressive residual stresses near the surface. The bending fatigue strength of gas carburized specimens was showed to decrease with the increasing case depths caused by the increasing of internal oxidation and nonmartensitic transformation present at the surface.     

冷轧板形优化规程算法的探讨

讨论冷轧板带板形优化规程的数学模型和计算问题,探讨了板形优化规程求解过程中的主要困难,给出了一种快速解法。     

弹簧卡箍多工位级进模设计

介绍了一种利用侧刃初定位,导正钉精定位的多工位级进模具的设计.该模具的上下模固定板具有高精度和长寿命,可快速更换凹模镶块,重复装配精度高,卸料板上安装了弯曲上模,卸料板既可弹性压料又可刚性卸料.