Ah-Der Lin

The Effect of Tooth Wear on the Vibration Spectrum of a Spur Gear Pair

In this paper, the effect of tooth wear on the vibration spectrum variation of a rotating spur gear pair is studied. In order to approximate the dynamic characteristics of an engaging spur gear pair, the load sharing alternation, position dependent mesh stiffness, damping factor and friction coefficient are considered in the mathematical model. The wear prediction model proposed by Flodin et al. is used to simulate the tooth profile wear process. The variation of the vibration spectra introduced from the interaction between the sliding wear and the dynamic load is simulated and analyzed. Numerical results indicate that the dynamic load histogram of an engaging spur gear pair may change greatly with the tooth wear. This finding implies that the variation of the gear vibration spectrum might be used to monitor the tooth wear of an engaging spur gear pair.

The Surface Absorption Coefficient of S304L Stainless Steel by Nd:YAG Micro-Pulse Laser

The surface absorption coefficient of S304L stainless steel during Nd:YAG pulse laser welding process was derived by using the inverse engineering technique. The thermal-elastic-plastic finite element method is employed to calculate the temperature distribution, melting pool depth and shape with specific heat source. The derived melting pool depths and diameters with different values of absorption coefficient were compared with experimental results. In this study, the least square error method is used to obtain the equivalent absorption coefficient. The results show that the equivalent absorption coefficient of S304L stainless steel is in the range of 0.1~0.25 for low power intensity Nd:YAG impulse laser welding.

Dynamic Responses of a Globoidal Cam System

Dynamic equations of the intermittent-motion of a globoidal cam driven system were derived in this study. The effects of roller mesh flexibility and cam profile curve on the residual vibration of a globoidal cam system were studied experimentally and numerically. Time varying roller mesh stiffness and damping coefficients were used to account for the periodic variation of the mesh stiffness in the dwell and the active periods respectively. Dynamic responses of a globoidal cam system in the active and the dwell periods were simulated and measured. The effects of cam profile and input shaft speed on the residual vibration were also studied in this work. Results indicated that the proposed model was feasible for the dynamic simulation of a globoidal cam system.

The Coffin-Manson formula for unleaded Sn/3.0Ag/0.5Cu solder

ABSTRACT This study explores Coffin-Manson equation and its feasibility for tin-silver-copper (Sn/3.0Ag/0.5Cu) solder. Most of the Sn/Ag/Cu solder studies were performed by experiment or the finite element method. In this study, MARC, a finite element analysis package, is applied for simulation. In the simulation, the material properties are temperature-dependent and the boundary conditions are time-dependent. Complying with JEDEC standard, the derivation of fatigue life formula for solder is built from experimental data. Using the experimental results of the BGA ball shear test, the amplitude of equivalent plastic shear strain at 1/4 cycle is obtained by finite element method. Meanwhile, substituting the CSP thermal cycle test results into Weibull life distribution, the amplitude of equivalent plastic shear strain at 3085 cycle is solved. The numerical results of the equivalent plastic shear strain amplitude are used to derive the Coffin-Manson equation proposed. To verify the feasibility and reliability of the formula derived, the result of an isothermal low cycle fatigue test is analyzed by the finite element method. It is observed that the proposed equation has a good agreement with the experimental data.

Determination of piezoelectric parameters from the measured natural frequencies of a piezoelectric circular plate

ABSTRACT Due to the complexity of electro-elastic coupling characteristics in piezoelectric materials, some elastic, dielectric and piezoelectric parameters are difficult to measure. Usually, these parameters are determined by assuming that all other parameters remain constant during the measurement. However, the interactive effect between material properties makes this assumption not always true. In this study, the measured natural frequencies of the specified circular piezoelectric plate are used to extract these parameters simultaneously. In other words, all these parameters are determined with consideration of the interactive electro-elastic coupling effect. The analytic model of a free-free circular piezoceramic plate was derived and solved to establish the relationship between natural frequencies and their material parameters. In order to cover most of the parameters, the out-of-plane (non-symmetric transverse) and in-plane (symmetric extensional) modes are considered. The genetic algorithm is employed to determine most of the elastic, dielectric and piezoelectric parameters from a least square error between the calculated and measured natural frequencies. The numerical results derived from the parameters proposed in this work reveal that they coincide well with the measured data. In other words, the proposed method for extracting piezoelectric parameters is both feasible and effective.

A study on the conductivity variation of au coated conductive particles in ACF packaging process

In the ACF packaging process, a bonding force will be applied to the ACF structure. The finite element analysis is used to simulate the ACF packaging process. Material behavior is assumed to be superelastic for resin, viscoelastic for polymer matrix, and elasticplastic for metal, such as bump, pad, chip, and Au-film. The axis-symmetric model is employed in FEA simulation with time-varying bonding force and operating temperature. In this study, the parameters, including conductive particle diameter, Au-film thickness, and bonding force, are analyzed with nonliner and temperature-dependent material properties. The simulation results indicate that bonding force and operating temperature have strong effects on the formation of concave on Au-film. In addition, surface wrinkle of Au-film will be induced by the bonding force. Both of the concaving and the wrinkling on Au-film will decrease the contact area between the conductive particle and the bump and the contact area between the conductive particle and the pad. Decrease of the contact area means increase of the total resistance for the ACF structure. The results show that the smaller the conductive particle diameter, the smaller the contact area. Generally, increasing the thickness of Au-film will decrease the contact areas, except at the Au-film thickness of 0.05 µm.

An Investigation on the Shear Toughness for Sn/3.0Ag/0.5Cu and Sn/37Pb Solder Ball Joints

Both experimental and numerical analyses into the shear toughness parameter for Sn/3.0Ag/0.5Cu and 63Sn/37Pb solder ball joints are performed. The ball shear tests are conducted at the loading speeds of 200μm/s and 300μm/s using ball joint specimens with diameters of 300, 600 and 760 μm. The failure behavior of the solder joints is quantified in terms of their fracture toughness. The results show that the shear toughness increases with an increasing solder ball diameter. Furthermore, it is shown that the Sn/3.0Ag/0.5Cu solder ball has a greater ductility than the eutectic 63Sn/37Pb solder ball. It is found that the shear toughness with great differentiability is relatively insensitive to the loading speed, and is therefore a suitable parameter with which to evaluate the ductility of solder ball joints in ball shear tests. Finally, the finite element analysis is further employed in the simulation with the software of MSC, Marc. Numerical predictions have good agreements compared with experiment ones.

A study on the double-beam laser scribing process for CIGS thin film solar cells

The finite element method has been employed to simulate the double-beam laser scribing on the Pattern 1 process of CuInGaSe2-based thin film solar cells (CIGS). The advantages of high concentrated power and manufacturing accuracy of laser beam have been used to remove the Mo thin film on the substrate. The thermal-elastic-plastic finite element models in company with temperature dependent material properties are applied to characterize the heating process during the laser scribing. The effects of laser scribing parameters, e.g. power, scribing speed, and the distance of two lasers, on the single-beam and double-beam laser scribing of Pattern 1 process are also studied in this work respectively. Three double-beam laser scribing processes with different speed have been proposed and investigated. The temperature and thermal stress distributions around the vaporizing pools during the scribing process have been simulated and studied. The distributions of residual stress induced in this scribing process have also been studied by employed the inactive elements method in MARC software.

Residual Stress and Bead Profile Analysis of Pulsed Nd:YAG Laser Lap Welding

The weld bead temperature distribution and shape during pulsed Nd:YAG laser lap welding are studied. A volumetric heat source model is derived to include the surface flux and the keyhole heat transfer effects in the pulsed laser lap welding process. The proposed pulsed laser heat transfer mode is employed in a simulation with the commercial finite element software Marc. The numerically computed results of the weld pool dimensions are compared with the experimental results. The comparison shows a good agreement between the simulated and measurement results, indicating that the proposed model is feasible. The results reveal that the pulse duration and spot pitch have considerable influence on the temperature field distribution and the residual stress distribution.

Shear Toughness Evaluation of Solder Joints for the Reliability Tests

The effects of isothermal aging and the thermal cycling loading on the shear toughness of different solder materials and ball sizes have been explored. The difference between shear toughness values of traditional Sn/37Pb eutectic solder ball joints and the lead free Sn/3.0Ag/0.5Cu solders are chosen for discussion. The experiment measurements under the ball shear test (BST) have been compared and studied for both solder joints. The fracture behaviors of the solder joints under the high temperature aging and thermal cycling testing are examined by scanning electron microscope (SEM). The variation of shear toughness of different ball joints reveals that the high temperature aging and thermal cyclic loading reduce the shear toughness significantly. The measured shear toughness values indicate that the Sn/3.0Ag/0.5Cu solder joints have better ductility for the joints undergoing the high temperature aging and the thermal cycle loadings. Based on the measured results, the better reliability for the Sn/3.0Ag/0.5Cu ball joints is expected, due to the aging and cycling load testing.