Note on non-linear bending of tapered cantilever beams

A simple numerical method is suggested to solve the exact bending equation for a slender non-uniform cantilever beam, loaded at the tip. Results are checked with available data in the literature.     

A study on fracture characteristic of structural adhesive at bonded specimen made by 3D printer

Journal of Mechanical Science and Technology - This study aims at investigating the fracture characteristics of adhesive used at double cantilever beam specimens made by 3D printers. The experiment...     

A study on the crashworthiness and rollover characteristics of low-floor bus made of sandwich composites

This paper describes the results of the numerical evaluation on crashworthiness and rollover characteristics of a lowfloor bus vehicle made of sandwich composites. The sandwich composite used for the vehicle structures was composed of aluminum honeycomb core and WR580/NF4000 glass-fabric/epoxy laminate facesheets. Material tests were conducted to determine the input parameters of the composite laminate facesheet model and the effective equivalent damage model for the orthotropic honeycomb core material. Crashworthiness and rollover analysis of the low-floor bus was conducted using the explicit finite element method (FEM) analysis code LS-DYNA3D with the lapse of time. The crash condition of the low-floor bus was a frontal accident with a speed of 60 km/h. Rollover analysis was done according to the safety rules of the European standards (ECE-R66). The angular and translation velocity and its angle with the ground just before impact for rollover were calculated using the dynamic analysis program. The results showed that the survival spaces for the driver and passengers were secured against frontal crashworthiness and rollover of the low-floor bus. In addition, the modified Chang-Chang failure criterion is recommended to predict the failure modes of the composite structures for crashworthiness and rollover analysis.     

On the dynamics of tapered vibro-impacting cantilever with tip mass

This paper explores nonlinear dynamic behavior of vibro-impacting tapered cantilever with tip mass with regard to frequency response analysis. A typical frequency response curve of vibro-impacting beams displays well-known resonance frequency shift along with a hysteric jump and drop phenomena. We did a comprehensive parametric analysis capturing the effects of taper, tip-mass, stop location, and gap on the non-smooth frequency response. Analysis is presented in a non-dimensional form useful for other similar cases. Simulation results are further validated with corresponding experimental results for a few cases. Illustrative comparison of simulation results for varying parameters brings out several interesting aspects of variation in the nonlinear behavior.     

Adhesive interface-peeling properties of tapered double cantilever beam bonded with dissimilar material under in-plane and out-of-plane shear conditions

In this study, the lightweight composite materials of carbon fiber-reinforced plastic, aluminum and aluminum foam were applied as three different bonding m     

A study on the characteristics of fracture resistance curve of ferritic steels

Fracture resistance (J-R) curves are used for elastic-plastic fracture mechanics analyses. The specimen geometry and the reversed cyclic loading affect the fracture resistance (J-R) curve. On the specimen geometry, The effects of specimen size plane size, specimen thinkness, side grooving and crack length were studied. On the reversed cyclic loading, the effects of load ratio and incremental plastic displacement were studied. The results revealed that theJ-R curves increased with increasing plane size and decreased with increasinga/W and theJ-R curves decreased with decreasing the load ratio and the incremental plastic displacement, respectively.     

IMPACT: a facility to study the interaction of low-energy intense particle beams with dynamic heterogeneous surfaces

The Interaction of Materials with Particles and Components Testing (IMPACT) experimental facility is furnished with multiple ion sources and in situ diagnostics to study the modification of surfaces undergoing physical, chemical, and electronic changes during exposure to energetic particle beams. Ion beams with energies in the range between 20 and 5000 eV can bombard samples at flux levels in the range of 10(10)-10(15) cm(-2) s(-1); parameters such as ion angle of incidence and exposed area are also controllable during the experiment. IMPACT has diagnostics that allow full characterization of the beam, including a Faraday cup, a beam imaging system, and a retarding field energy analyzer. IMPACT is equipped with multiple diagnostics, such as electron (Auger, photoelectron) and ion scattering spectroscopies that allow different probing depths of the sample to monitor compositional changes in multicomponent and/or layered targets. A unique real-time erosion diagnostic based on a dual quartz crystal microbalance measures deposition from an eroding surface with rates smaller than 0.01 nm/s, which can be converted to a sputter yield measurement. The monitoring crystal can be rotated and placed in the target position so that the deposited material on the quartz crystal oscillator surface can be characterized without transfer outside of the vacuum chamber.     

A study on penetration fracture characteristics of glass plates subjected to impact loadings

In this study, a comparison between theoretical solutions and experimental results are examined for fracture conditions in the case of float glass plates subject to static loadings. The ranges from fracture-generated initiations to critical penetration energies are confirmed according to the impactor mass under high velocity, and an analytical method is presented to determine the fracture strength and penetration strength. Also, fracture patterns are investigated according to impact velocities.     

A comparison of the microstructure of silicon nitride-silicon carbide composites made with and without deoxidized starting material

Two different types of silicon carbide (SiC) matrix composites, with either 10 wt% or 20 wt% silicon nitride (Si₃N₄) reinforcement, were fabricated to investigate the effect of pretreatment on the resulting composite micro-structure. The first type of composite was prepared from as-received α-SiC and α-Si₃N₄ powders, while the second type was prepared from powder compacts that had been deoxidized to eliminate surface silica on the powder particles. The composites were hot isostatically pressed in tantalum cans at 2373 K for 1h under a pressure of 200 MPa. Density measurements showed that full theoretical density was achieved for the composites prepared from the as-received powders, while much lower densities were obtained for the composites prepared from the deoxidized green compacts. Almost all of the α-SiC transformed into β-SiC, and almost all the α-Si₃N₄ transformed into α-Si₃N₄ in the composites made from the as-received powders, while in the composites made from the deoxidized material the α-SiC remained untransformed and both α-Si₃N₄ and β-Si₃N₄ phases were present in significant quantities. High-resolution transmission electron microscopy and Fresnel fringe imaging were used to identify the grain boundary and interphase boundary structure. Most interfaces were found to be covered with ? 1 nm thick amorphous intergranular films in the composites prepared from as-received powders, whereas most interfaces were found to be free of such amorphous intergranular films in the composites prepared from the deoxidized material. Taken together, the presence of intergranular films at the interfaces and the results from density measurements are consistent with the densification and reverse α → β-SiC transformation taking place in the composites made from as-received powders by a liquid-phase sintering route. An incomplete liquid-phase sintering mechanism is also able to explain the microstructure observed in the composites made from the deoxidized material.     

超高强度钢制航天气瓶断裂安全性评价方法的试验研究

从超高强度钢应力腐蚀门槛值的测试方法入手,通过试验研究分析了过载技术对改善超高强度钢应力腐蚀性能的重要作用,以确定合理的过载规范,解决NASA推荐的方法中进行验证试验所需验证应力系数过大的问题,为制定气瓶的断裂安全评价方法指出方向。     

A numerical study on the impact response and energy absorption of tapered thin-walled tubes

Tapered tubes have been considered desirable impact energy absorbers due to their relatively stable mean load–deflection response under dynamic loading. Relatively few studies have been reported on the energy absorption performance of tapered tubes compared with straight tubes. This paper compares the energy absorption response of straight and tapered thin-walled rectangular tubes under both quasi-static and dynamic axial impact loading, for variations in wall thickness, taper angle, impact mass and impact velocity. It is found that the dynamic response of tapered tubes is more sensitive to impact velocity and wall thickness than taper angle for lower impact velocities. Inertia effects influenced the dynamic response for both straight and tapered tubes, yet were less significant for the latter. Overall, the results indicate that the energy absorption response of tapered tubes can be controlled via their wall thickness and taper angle, and this highlights their potential for use as energy absorbers. Analysis has been undertaken using a finite element model, validated using existing theory.     

A study of the physical adhesive state between solids

The force required to separate two adhering bodies (needles with plates) was measured for various materials. The contact pressure was controlled by the heat expansion of a liquid. The adhesion force obtained from a load of less than 5 mgf was a constant value depending on the type of material. It was found that the adhesive energy was affected largely by temperature and could be expressed by an Arrhenius relation. From the results obtained the Hamaker constant was estimated to be (1– 3) × 10⁻¹² erg.     

A facility for measuring the static characteristics of high-intensity electron beams

The operating principle of a versatile facility for measuring the static parameters of high-intensity electron beams is based on detecting transient radiation produced by ribbon-shaped and axially symmetric electron beams incident on a metal target. Schemes for detection of transient radiation are discussed, and features of the measurement procedures suitable for particular beam configurations are described. For the first time, the design of an analyzer of ribbon-shaped electron beams is presented. The usability of the facility is confirmed by experimental results and numerical calculation.     

An optimum study of the anticlastic deformations of strips with tapered edges

If the edges on the concave side of an elastically bent strip are tapered, the anticlastic deformations of the cross sections can be greatly reduced. This paper concerns the calculation of the specific dimensions of the tapers which will reduce the deformations of the cross sections to a minimum when the strip is bent to a prescribed radius.The optimum tapers are obtained by a Newton-Raphson iteration process, together with a parametric study. The results are presented in tabular form for Poisson's ratio values of 0.3–0.5. It is shown that the maximum relative displacements of the bent strips can be reduced by as much as 60–95 per cent by suitably tapered concave edges.     

A study on the flow characteristics of butterfly valve with baffles

Journal of Mechanical Science and Technology - In the industry, globe valves, which are commonly used to precise control the flow rate along with opening and closing flow in pipes, are technically...     

A study on the finite element preprocessing for the analysis and design with discontinuous composites

A strategy of finite element (FE) preprocessing of discontinuous fiber or whisker reinforced composite materials for mechanical analysis and design has been treated in this paper. The procedures were based on the calculation of the error in energy norm for global convergence and the traction differential approach at fiber/matrix interface for local convergence. The mesh refinement strategy was intended to theh-based generalized approach using the elongated element at the fiber/matrix interface, which yields significantly different patterns from those obtained by conventional mesh refinement procedures. This difference may have a critical bearing on the subsequent thermo-mechanical properties predicted by the finite element analysis (FFA). It was found that the FE mesh design of adequate element aspect ratio at the fiber/matrix interface results in a much more rapid computational convergence rate than that obtained by the conventional approach.     

A study on fracture behaviors of aluminum and CFRP jointed with pin

Weight reduction has been acknowledged in the automotive industry. Particularly, the weight reduction of automotive body is an ecofriendly technology development, as the corresponding fuel consumption or amount of gas polluting the atmosphere is greatly reduced. As a substitute light-weight material, Aluminum is frequently employed while there is CFRP (carbon fiber reinforced plastic) as the most highlighted material in the future. However, one of the problems is concerned with the coupling of light-weight materials. Particularly, in the case of CFRP having a certain fiber structure orientation, the direction perpendicular to fibers exhibits the disadvantage although each direction of fiber has great advantages in the durability and mechanical properties. Therefore CFRP materials will lose advantages of the material when holes or cracks have occurred in the material. Thus, in this study, mechanical characteristics occurring in stationary parts and cracked parts were investigated by producing holes and cracks in the center of the specimen fixed by a pin by using aluminum-6061, CFRP for woven type, and CFRP for unidirectional type. Also, experimental result data were confirmed by using the finite element analysis method and the verification was made by comparing the data corresponding with experimental data. The structural analyses were performed with the design of fiber structure and the lamination process was used for a more accurate design of CFRP. As experiments were performed by conducting with a universal tester by SHIMADZU Company of AG-X 50 kN, the reliabilities of analyses were verified.     

湿式双离合自动变速器起步控制策略的研究

简要介绍了湿式双离合自动变速器的结构和工作原理,提出了起步过程的评价指标,重点分析了起步过程的控制策略,阐述了单离合和双离合两种起步方式,并搭建了试验台架,对两种起步方式进行了试验研究。     

Distinguishing the effects of adhesive wear and thermal degradation on the tribological characteristics of paper-based friction materials under dry environment: A theoretical study

Adhesive wear and thermal degradation are the main aging mechanisms of paper-based friction materials. However, how these aging mechanisms affect the tribological characteristics of such materials is not fully understood. In this paper, the respective influences of the two aging mechanisms on the tribological characteristics of the friction materials are investigated through simulation. It is assumed that adhesive wear pre-dominantly affects the surface topography, while thermal degradation significantly affects the mechanical properties of the friction material. The simulation results show that the static friction coefficient and both normal and tangential contact stiffnesses increase due to adhesive wear, but decrease due to thermal degradation. These trends are qualitatively in agreement with experimental observations reported in the literature and our previous work.     

Experimental study on adhesive wear of milling insert with complex groove

This paper presents an experimental study on the adhesive wear of a milling insert with complex groove when milling 3Cr-1Mo-1/4V and 0Cr18Ni9 steels. Experimental measurements of milling temperature and milling force were performed. Then the adhesive behaviors and mechanisms between the steels and uncoated carbide were analyzed and discussed. It is found that the high temperature gradient, thermal stress, alternate compressive stress, and tensile stress in cut-in and cut-out, provide a situation for adhesion. Some suggestions for avoiding adhesive wear and the mechanism of adhesive wear of the insert are presented.