Applied Mechanics and Materials Vols. 446-447

Abstract: For mine mining, In-situ stress is the fundamental force that causes the deformation and failure of surrounding rock in the mining engineering and supporting, and produces mine dynamic phenomena. Among many factors which affecting the stability of mining engineering, In-situ stress is the main and one of the most fundamental factors. According to the In-situ stress monitoring method some coal mine adopted, this paper introduces the concrete principle and working process.

Abstract: This study is based on those data gathered on a 450m-long railway with a VRS GPS. In addition, certain location data on a railway were gathered through three 'Continuous VRS GPS' measurements and one 'Stop & Go VRS GPS' measurements while a railway-maintenance vehicle with GPS receivers mounted on its left & right sides was moving, Based on these location data, an average inter-rail space was analyzed. As a result of the analysis, the inter-rail space ranged from 1480mm to 1530mm. Based on the standard design dimension of an inter-rail space equal to 1,500mm and the average VRS GPS accuracy of ±3cm permissible in South Korea, the range was acceptable. Furthermore, if the center of a GPS receiver is placed over the vertical line of a rail center, more accurate location data on the railway could have been gathered.

Abstract: This paper developed a resistivity measurement system on the platform of in-situ detector which based on seafloor drilling machine. In order to precisely process the weak voltage signal which outputted by the resistivity probe, the paper carried out the cross-correlation algorithm theoretical derivation and MATLAB simulation, then ported the algorithm to TMS320F28069 DSP processor and designed hardware. A mass of contrast experiment shows that the cross-correlation algorithm is an effective method to process weak signal. It can improve accuracy and anti-jamming ability of the submarine sediment resistivity measurement system. The method of submarine sediment resistivity measurement can be widely used in fields of marine geological survey, marine environment research, etc.

Abstract: This report described the Impact Test result and Bioactivity Properties of biodegradable Polycaprolactone (PCL) blend with nano- Montmorillonite (MMT) and Hydroxyapatite (HA). The amount of nano-MMT is varies from 2 to 4 by weight % meanwhile the amount of HA is fixed to 10 by weight percentage (wt%). The addition of nano-MMT and HA filler is to tune and indirectly improve the mechanical and bioactive properties of PCL. The samples for these test are injected from injection molding machine. The Impact test are conducted using Charpy Method. From the analysis it is found that the toughness of PCL are decreased by the addition of these fillers. PCL/MMT composites gives a better result compare to PCL/MMT/HA composites. This is due to the HA characteristic which is brilttle and tends to reduce the ductile properties of the polymer. From the Simulated Body Fluis (SBF) result, formation of apatite layer at the surface of the composites is evidence of excellent bioactivity properties of HA. The enhance of bioactivity has been proved while incorporation of HA into PCL/MMT composite. SEM-EDX image showed the bulk formation of apatite layers on the composite surface with 10 wt% HA after 3 days immersed in SBF solution.

Abstract: Friction at the interface of die and workpiece plays an important role in metal forming. This paper introduces measurement methods of friction coefficient at curved surface in recent years, and divides the friction coefficient measurement methods into direct measurement methods and indirect measurement methods. Furthermore, the working principles and technical characteristics of these methods are explained.

Abstract: A variable structure attitude control system design method that guarantees the finite-time stability is proposed for hypersonic vehicle attitude control. According to the characteristics of the hypersonic vehicle longitudinal attitude model, it is considered to comprise attack angle control loop and angular rate control loop. The attack angle controller and pitch angular rate controller based on variable structure control are designed respectively which ensure the finite-time stability. The finite-time stability of the whole attitude control system has been proved .The simulation results illustrated that the proposed attitude controller has good rapidity and robustness.

Abstract: Applying the principles of electro-pneumatics (EP) in food and beverage industries with the integration of timer and counter in a motion sequence control. Double acting cylinders are utilized in this study that will properly simulate the effect of different electro-pneumatics control systems. Forward motion sequence control directed the entire EP circuits and piston rod’s operation speed are controlled. The sensing information of all linear actuators is carried out by limit switches or electrical rollers that sense whether an extension or retraction has occurred. This information is passed to different relays such as counter relay, relay with switch-off delay and relay with switch-on delay.

Abstract: Teleoperation means operating a vehicle or a system remotely over a distance.Teleoperation extends human capabilities to perform tasks remotely by providing the operator withsimilar conditions as those at the remote location. Generally, operator should be supported inreal-time with an accurate data about the teleoperation environment. This paper proposes atime-delay compensation algorithm for environment construction to modify the well-developed BITAGV to be teleoperated. This Algorithm includes predicting the vehicle position in the future timeusing Model Predictive control (MPC). Then, environment is constructed according to this positionusing the Laser scanner. Real and simulation experiments are presented to illustrate the performanceand effectiveness of the algorithm in compensating time-delay for Teleoperation.

Abstract: This paper firstly analyzes traditional NC machining simulation technique and its flows. On this basis, it puts forward a method that implements NC machining three-dimensional simulation and emulation system architecture using distributed object CORBA component technology and OpenGL graphic technology [1,2], and details information about the model of this architecture, use Visual C++ as developer tool to implement NC machining simulation which is independent of platform and network.

Abstract: Vibration properties of most assembled mechanical systems depend on frictional damping in joints. The nonlinear transfer behavior of the frictional interfaces often provides the dominant damping mechanism in structure and plays an important role in the vibratory response of it. For improving the performance of systems, many studies have been carried out to predict measure and enhance the energy dissipation of friction. This paper presents a new approach to vibration reduction of flexible spacecraft with enhancing the energy dissipation of frictional dampers. Spacecraft is modeled as a 3 degree of freedom mass-spring system which is controlled by a lead compensator and System responses to step function evaluated. Coulomb and Jenkins element has been used as vibration suppression mechanisms in joints and sensitivity of their performance to variations of spacecraft excitation amplitude and damper properties is analyzed. The relation between frictional force and displacement derived and used in optimization of control performance. Responses of system and control effort needed for the vibration control are compared for these two frictional joints. It is shown that attitude control effort reduces, significantly with coulomb dampers and response of system improves. On the other hand, due to stick-slip phenomena in Jenkins element, we couldn’t expect the same performance from Jenkins damper.