FINITE ELEMENT ANALYSIS ABOUT STRESS AND STRAIN OF SURFACE PEELING IN Cu-Fe-P SHEET

The microstructure of surface peeling in finish rolled Cu-0.1Fe-0.03P sheetis analyzed by scanning electron microscope and energy dispersive spectroscope. Fe-rich areas ofdifferent contents are observed in the matrix. The stress distributions and strain characteristicsat the interface between Cu matrix and Fe particle are studied by elastic-plastic finite elementplane strain model. Larger Fe particles and higher deforming extent of finish rolling are attributedto the intense stress gradient and significant non-homogeneity equivalent strain at the interfaceand accelerate surface peeling of Cu-0.1Fe-0.03P lead frame sheet.

Ultrasonic Welding of Magnesium–Titanium Dissimilar Metals:A Study on Thermo-mechanical Analyses of Welding Process by Experimentation and Finite Element Method

Ultrasonic welding is an effective ways to achieve a non-reactive/immiscible heterogeneous metal connection, such as the connection of magnesium alloy and titanium alloy. But the thermal mechanism of magnesium alloy/titanium alloy ultrasonic welding has not been defined clearly. In this paper, the experimental and the finite element analysis were adopted to study the thermal mechanism during welding. Through the test, the temperature variation law during the welding process is obtained, and the accuracy of the finite element model is verified. The microscopic analysis indicates that at the welding time of 0.5 s, the magnesium alloy in the center of the solder joint is partially melted and generates the liquid phase. Through the finite element analysis, the friction coefficient of the magnesium–titanium ultrasonic welding interface can be considered as an average constant value of 0.28. The maximum temperature at the interface can exceed 600 ℃ to reach the melting point temperature of the magnesium alloy. The plastic deformation begins after 0.35 s and occurs at the magnesium side at the center of the interface.

Analysis of stress-magnetic coupling effect in weak magnetic environment

Metal magnetic memory （MMM） signals are difficult to be analyzed due to noise interfer- ence, which limits its practical engineering application. A method of improving the magnetic signals is proposed in this paper by placing the excitation device which generates a weak external magnetic field about 100 A/re. The effect of the external magnetic field on the magnetic signals is studied using both finite element method （FEM） and uniaxial tensile tests. Comparison of the test data with the simulation ones of stress-magnetic coupling shows that the magnetic signals are strengthened and the measurement sensitivity of the detection system is greatly improved through the external magnetic excitation. Moreover, the FEM result has a good agreement with the testing results of No. 20 steel plate. The proposed method has laid a foundation for further practical engineering application.

Finite element analysis of stress corrosion cracking for copper in an ammoniacal solution

Finite element analyses including a cohesive zone model （CZM） were conducted to investigate the role of corrosion product films （CPFs） in stress corrosion cracking （SCC） for copper in an ammoniacal solution. It is found that a tensile CPF-induced stress generates near the interface between the CPF and the copper substrate at the substrate side in front of the notch tip for a U-shaped edgenotched specimens. The CPF-induced stress is superimposed on the applied stress to enhance emission and motion of dislocations. The peak opening stress （S11） increases with an increase in CPF thickness and a decrease in CPF Young＇s modulus. Damage mechanics based on the CZM was applied to study the stress corrosion crack initiation and propagation by analyzing the stress redistributions and load-displacement curves. The results show that the crack initiates first in the CPF and then propagates to the copper substrate. The fracture strain of the specimen covered a CPF is lower than that without a CPF. Based on the simulation results, the mechanism of the CPF-induced SCC, which promoted the initiation and propagation of the stress corrosion cracks, was discussed.

Research on FBG-Based CFRP Structural Damage Identification Using BP Neural Network

A damage identification system of carbon fiber reinforced plastics （CFRP） structures is investigated using fiber Bragg grating （FBG） sensors and back propagation （BP） neural network. FBG sensors are applied to construct the sensing network to detect the structural dynamic response signals generated by active actuation. The damage identification model is built based on the BP neural network. The dynamic signal characteristics extracted by the Fourier transform are the inputs, and the damage states are the outputs of the model. Besides, damages are simulated by placing lumped masses with different weights instead of inducing real damages, which is confirmed to be feasible by finite element analysis （FEA）. At last, the damage identification system is verified on a CFRP plate with 300mm × 300mm experimental area, with the accurate identification of varied damage states. The system provides a practical way for CFRP structural damage identification.

A comparison between friction stir welding, linear friction welding and rotary friction welding

Three friction welding processes are compared for temperature, stresses and strains, as well as strain rates developed in the early phases of the processes, which are essential in their successful development. These are friction stir welding （FSW）, linear friction welding （LFW） and rotary friction welding （RFW）. Their common characteristic is the use of friction to generate adequate energy and raise temperature locally in order to create favorable conditions for welding at the interface between two parts. Although the mode of movement is different for each one of them, welds are produced through plastic deformation. The Lagrangian and coupled Eulerian-Lagrangian numer- ical models developed have produced results which are in qualitative agreement with experiments and have shed a light on the commonalities of these friction welding processes

Particle fracture and debonding during orthogonal machining of metal matrix composites

This paper investigates the particle fracture and debonding during machining of metal matrix composite （MMC） due to developed stress and strain, and interaction with moving tool by finite element analysis. The machining zone was divided into three regions： primary, secondary and tertiary deformation zones. The tendency of particles to fracture in each deformation zone was investigated. The findings of this study were also discussed with respect to the experimental results available in the literature. It was found that particles at the cutting path inthe tertiary deformation zone fractured as it interacted with tool. In the secondary deformation zone, particles interacted with other particles as well as cutting tool. This caused debonding and fracture of huge number of particles as those were moving up along the rake face with the chips. No particle fracture was noted at the primary deformation zone. The results obtained from finite element analysis were very similar to those obtained from experimental studies.

A versatile electrostatic trap with open optical access

A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking NDa molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 inK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.

Advances in numerical computation based mechanical system design and simulation

This paper highlights the available numerical computation techniques in mechanical engineering field with focus on application of modeling and simulation within renewable energy conversion machines as a particular research case. The study makes special focus on simulation approaches based on finite elements and multibody dynamics that are currently focused within the research community. Developing the simulation model in a computer-aided design （CAD） tool is a precondition for a successful simulation-based mechanical system research. The article discusses and elaborates the methods imple- mented to integrate design data with other computer-aided engineering functions. The motivation is the fact that simulation-based research is useful for design optimization of mechanical systems that operate in harsh and unfriendly environment where conducting physical testing of proto- types is difficult. In addition, the manufacturing environ- ment is benefiting from the developments in numerical computation techniques through machining simulation that significantly reduce the time-to-market and thus increase competitiveness. The study is also intended to explore the existing gaps of capabilities in current approaches in application of computational techniques in order to draw at- tention to future challenges and trends.