Applied Mechanics and Materials Vols. 184-185

Abstract: Aimed at the difficulty of rotary parts of complex curved surface in modeling and NC machining, making full use of advanced modern molding technology of Solidworks and powerful NC machining skill of Mastercam, the paper introduced a strategy , segmented milling that a true part was step to step machined by end mill not ball mill on 3 Axes NC milling machine but 4 Axes during rough machining. According to the method, it can raise the operation rate and shorten production cycle.

Abstract: Due to the micro-machined processes, there is residual stress in device layer of capacitive SOI accelerometer, which results in the deformation in sensing structure and hence, makes the device fail to work. To cope with the problem, based on the stress and stress gradient in device layer, in light of the mechanics theory and by dividing the proof -mass into several continuous varied cross-section beams, utilizing symmetric continuous conditions and deformation compatibility, a stress and deformation mechanics model of sensing structure in SOI accelerometer is proposed. By the comparison between the model and experiment data, which is obtained SOI device layer 50 μm and oxide layer 5 μm and model, it is indicated that the model could basically describe the sensing structure deformation. The model could hopefully be helpful in further exploration on stress and deformation in MEMS structure.

Abstract: A change in hub geometry with the aim of reducing or even removing the stress concentrations that appear in interference fits is proposed. This modification consists in including a chamfer in the hub. Stresses distributions and stresses concentrations factors are analyzed as a function of parameters that define the hub geometry with the aim of optimizing the design of proposed modified hubs.

Abstract: Stress intensity factors are calculated for a cracked plate reinforced locally subject to mode I loading. The stiffeners are considered to have both longitudinal and transverse stiffness. There is no relative displacement between the plate and the stiffener. It is considered that the shear stresses are lumped at a finite number of locations, the result is obtained by summation. The influence of the stiffener location and the stiffener relative stiffness on cracked plate is included. The stress intensity factor depends on all these factors. Case study shows that the shear stress acting parallel to the stiffener gives more effect on the stress intensity factor than the shear stress acting perpendicular to the stiffener. To increase the relative stiffness of stiffener avails to reduce the stress intensity factor of the cracked plate.

Abstract: Data transmission antenna plays an important role in transmitting data from satellite. The structure of antenna consists of four parts, including a feed tube, a reflecting surface, a brace and a adapter. Due to the unreasonable structure design and coarse mechanical analysis, the initial data transmission antenna was broken at the corner of a spiral in the process of random vibration test. In this paper an improvable method is brought up and mechanical analysis is carried out, the result shows that the first frequency raises from 324Hz to 328Hz and the stress root mean square decreases from 62MPa to 37MPa in X-direction random vibration. Of course, the improved antenna passes the random test.

Abstract: Finite element model of Cross wedge rolling asymmetric shaft is established, contrasting with symmetrical rolling, the axial relative displacement of weak-side and strong-side’s metal in asymmetric cross wedge rolling is analyzed. The results show that: axial relative displacement asymmetrical rolling on the weak-side undergo the process of “increase-decrease-unchangeableness” and axial non-uniform deformation increases; axial relative displacements on the strong-side undergo the process of “decrease- unchangeableness” and axial non-uniform deformation decreases. The results provide a theoretical basis for the cross wedge rolling asymmetric shaft parts.

Abstract: Strain distribution is crucial for understanding tube bending and preventing defects. In this paper, taking 321 stainless steel as the objective, via etched grid method, the strain distribution characteristics during tube bending are studied, the effects of the bending velocity and the bending angle on the strain distribution are analyzed, and the consistency of thickness strain with wall thickness variation is verified. The results show that: (1) three-dimensional (3D) strain is symmetrically distributed about bending plane and reaches the maximum value at wall extrados and intrados; (2) absolute value of the 3D strain increases at first, then decreases in tube bending; (3) compared with bending angle, bending velocity has greater effect on spatial strain, and compared with tangent strain, thickness strain is more sensitive to bending velocity; (4) thickness strain distribution characteristics are generally consistent with distribution characteristics of wall thinning degree.

Abstract: Stoppers are commonly used to improve the shock resistance of MEMS devices. However, the collision between MEMS structure and stoppers in shock environment may lead to emergence of the stress wave, resulting in the failure of devices. Therefore, MEMS devices designed based on current statics theory is unreliable. After analyzing the method and principle for MEMS reliability design, the shock dynamics model was established. Based on the model, the response of the traditional design and designs with different stoppers to shock was researched. At last, protection performances of different stoppers were evaluated. Results showed that the use of stoppers could improve the shock resistance of the device obviously, but hard stoppers would cause to the emergence of the sharp stress wave. Elastic stoppers had excellent protection ability which could strengthen the shock resistance of the device greatly.

Abstract: The terminal speed of wheel/rail train is being concerned in the era of high-speed train. The number of terminal speed represents development level of wheel/rail train. In this study, the calculation formulas of basic resistance and calculation adhesion of the "Harmony" EMU were used. It was assumed that the traction power is enough large, and the terminal speed of high-speed train was obtained by calculating for dry rail surface and humid rail surface. The average terminal speed was calculated by the area-method. Randomly variational adhesion coefficient was simulated, and the necessary and sufficient conditions for the terminal speed were derived.

Abstract: Structural damage intelligent diagnosis is the detection and evaluation of the structure, to make sure whether there is damage, and to figure out the position and the depth of the damage. The appearance of the damage affects the dynamic properties of the structure and leads to the reduction of the natural frequency and the change of the vibration mode. This paper mainly focuses on the damage diagnosis of the cantilevered machine tool beam, which includes parameterized modeling and modal analysis to get five natural frequencies and five vibration modes of different positions and different depths of the damage. The BP neural network is trained with the data base to realize the intelligent diagnosis.