Applied Mechanics and Materials Vol. 192

Abstract: A drying experiment of litchi pulp was done with a self-built heat-pump drying system. A few commonly-used thin-layer drying models for foods were linearized and fitted with the drying experimental data to select a relatively optimal model of depicting the relationship between moisture ratio and drying time of the heat-pump drying of litchi pulp. It was found that the Page model is relatively optimal. The multivariate linear regression approach was employed to solve for the parameters of the Page model based on experimental data and an experimental verification was conducted; the verification results show that the predicted values of the Page model have a good fitness with the measured values and thus the Page model can predict more accurately the moisture ratio and drying rate of litchi pulp in a heat-pump drying process.

Abstract: Based on the maximum likelihood method, this paper analyzed the influence of tailplane icing on aerodynamic parameters by parameter identification. A nonlinear longitudinal flight dynamics model for aircraft was built, and an identification system was constructed using maximum likelihood method. According to the flight test data of DHC-6 aircraft, the aerodynamic parameters of clean aircraft and two different cases of iced aircraft with particular ice shapes on the tailplane were identified. Eventually, the results of the identification show that the tailplane icing has several adverse effects on the aircraft flight characteristics, including flight performance, elevator effectiveness, stability and safety.

Abstract: An improved model for heat transfer process is established to study the ice accretion on airfoil, which takes into consideration the influence of conduction through ice and water film compared with the classical Messinger model. Incorporating the calculation of collection efficiency by the Eulerian two-phase theory, ice accretion in specific condition on a NACA0012 airfoil is simulated with the classical model and the improved model respectively. It is shown that the simulation result with the improved model agrees well with experiment data, and the model is demonstrated to be valid in ice shape prediction and complement the shortage of the Messinger model in the estimation of freezing fraction in glaze ice condition, especially in the initial stage of ice accretion.

Abstract: Noise caused by vibration in ship’s seawater piping system can easily transfer outboard. This will destroy the stealth of some military ships for especial purpose. In this paper, experiments were carried out to investigate the pipe vibration under the prompting of seawater pump in a testing platform. The vibration transmission character along pipeline is researched and the isolation effects of shock absorption bracket and flexible rubber bellows were analyzed. Based on the results, some advices were given for the vibration resisting of the seawater piping system.

Abstract: According to regenerative chatter theory, this paper abstracts the machining process of XXX machine as a mathematical model firstly. The main process is end milling, so this paper abstracts the machine as an end-milling mathematical model, a delay motion equation with 2-DOF. All parameters of this equation can be acquired by modal analysis. Then SIMULINK model is created based on the mathematical model. According to the response characteristics of simulation analysis system, the method of determining threshold of steady area is acquired.

Abstract: A failure analysis has been conducted on a diesel engine crankshaft used in a commercial vehicle, which is made from 42CrMo forging steel, and the crankshaft was after induction hardening process. The fracture occurred between the 4th journal and the 4th crankpin, fracture section indicates that fatigue is the dominant mechanism of failure for this crankshaft. In order to find the failure causes, the dimension of journal boss fillet, material chemical compositions, surface hardness and depth of hardness layer were evaluated. Chemical compositions of crankshaft material, surface hardness and the depth of hardness layer are within the specified range, however the dimension of journal boss fillet is less than specified, and the transition zone of hardness layer was found on the journal boss fillet. Heavy segregation and many non-metallic inclusions aggregate zones were found from metallographic, these would lead to the reduction of endurance bending strength. FEA analysis results suggest that the dimension of journal boss fillet have an important effect on the stress and stress amplitude of the crankshaft. So the disqualification machining and material property are the main causes for the crankshaft fatigue fracture.

Abstract: For the production of high reliability, wide use range, low cost of the bending deflection of pipe test bed, the design of test program was optimized, the structural design. Design of experiment platform to meet the requirement of experiment, and has practical application value.

Abstract: It is a controversial topic that the reference relationship between ideal distance of the shot putting and practical training. This paper analyzes the optimal release angle and its practical limitation of ideal model, by principles of mechanics, building mathematical model by deduce of mathematics and physics and according to the practical features of Kinesiology. The results demonstrate, the optimal release angle can only act as the quantitative index for teaching and training, not the optimal results of training and competition. During the teaching and training, according to the reality, relating to self-feature of athletes, use the reasonable parameters, so as to benefit for technology and training in order to improve the grades of athletes.

Abstract: In modern football games, a player's skill to lob for the goal is no less than critical as sometimes it is the difference between victory and defeat. In the process of executing a lob shot, following factors are to determine whether the shot is going to be successful: Distance from ball to goal—a, distance from the player to goal—b, height of the goal—h, maximum height the goalkeeper can reach—h, initial velocity of the ball V0, horizontal angle (emergence angle), air resistance and whether the goalkeeper moves in the process. In search of the ideal position to lob, the thesis has three discussions with models established respectively

Abstract: To decrease the probability of severe accidents for the stream boiler, a kind of preventive maintenance named operational check based RCM (Reliabilty Centred Maintenance) is put forward to reduce the probability of multi-ply failure occurrence caused by the covert failure, which can reduce or hold back the occurrence of severe accident. The instance is given to describe the influence of the preventive maintenance named operational check for the occurrence probability of severe accident. The instance indicates that the occurrence probability of severe accident will greatly reduce, so this method is useful for machine management.