Effect of Microstructure Size on Deformation Kinetics and Thermo-Mechanical Fatigue of 63Sn37Pb Solder Joints

1996 ◽  
Vol 118 (2) ◽  
pp. 49-54 ◽  
Author(s):  
Zhenfeng Guo ◽  
Hans Conrad
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Cooling Rate ◽  
Room Temperature ◽  
Boundary Area ◽  
Deformation Kinetics ◽  
Mechanical Fatigue ◽  
Creep Stress ◽  
Boundary Sliding ◽  
Creep Stress Exponent

An increased cooling rate following reflow produced a decrease in the microstructure size including the size of the colonies, the Pb-rich dendrites and the eutectic phases. The decrease in microstructure size gave an increased creep rate at room temperature and a decrease in the creep stress exponent. Also, thermo-mechanical fatigue crack growth rate decreased and fatigue life increased with the decrease in microstructure size. These effects of the increased cooling rate were attributed to an increase in boundary sliding which could occur from the increase in boundary area with decrease in microstructure size.

Measurement of Press Creep Stress Exponent of ZM6 Alloy at Room Temperature

2007 ◽  
Vol 546-549 ◽  
pp. 509-511
Author(s):  
Ying Ying Zhong ◽  
Shu Fang Xu ◽  
Xin Ming Zhang ◽  
Tian Cai Guo ◽  
Yun Lai Deng
Keyword(s):  
Strain Rate ◽  
Linear Relationship ◽  
Stress Exponent ◽  
Room Temperature ◽  
Constant Load ◽  
Nano Indentation ◽  
Indentation Technique ◽  
Creep Stress ◽  
Creep Stress Exponent ◽  
Relationship Of

Nano-indentation technique was used to survey creep stress exponent of ZM6 (Mg-2.8Nd-0.7Zn-0.6Zr) alloy at room temperature. The results showed that average press creep stress exponent of ZM6 alloy was about 89.75, and independent of strain rate and hardness, which has been verified by linear relationship of the double logarithmic plots between strain rate ( ε& ) and hardness (H ) measured by a nano-indentation equipment with constant load of 500mN.

Inverse Hall-Petch Effect of Hardness in Nanocrystalline Ta Films

2011 ◽  
Vol 378-379 ◽  
pp. 575-579 ◽  
Author(s):  
Zhen Hua Cao ◽  
Xiang Kang Meng
Keyword(s):  
Grain Size ◽  
Room Temperature ◽  
Creep Property ◽  
Atomic Diffusion ◽  
Creep Stress ◽  
Dominant Deformation Mechanism ◽  
Creep Stress Exponent ◽  
Room Temperature Creep ◽  
Feature Scale ◽  
Indentation Response

Hardness and creep property of nanocrystalline Ta films were studied by nanoindentation tests. Experimental results suggested that hardness decreases with the decrement of grain size, which exhibits an inverse Hall-Petch effect. A remarkable room temperature creep behavior of nanocrystalline Ta films was revealed during indentation response. Creep stress exponent decreases with the decrement of feature scale, such as grain size and indent displacement. Grain boundary (GB) mediated process involving atomic diffusion and the emission of dislocation at GB is believed to be the dominant deformation mechanism.

Threshold and Low-Rate Fatigue Crack Growth of a NiMoV Rotor Steel

1981 ◽  
Vol 103 (2) ◽  
pp. 104-111 ◽  
Author(s):  
T. T. Shih ◽  
J. K. Donald
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Room Temperature ◽  
Stress Ratio ◽  
Threshold Region ◽  
Rotor Steel ◽  
Low Rate

An automated, computer-controlled K-decreasing technique was used to determine the threshold, ΔKth, and low-rate fatigue crack growth of a NiMoV rotor steel. A more conventional K-increasing technique was also used. Excellent agreement between results obtained from both techniques was observed. For the material and environment studied, no crack arrest was observed for crack growth rate down to 2.5 × 10−8 mm/cycle (10−9 in./cycle). As such, an operational definition of ΔKth was defined as the stress intensity factor range corresponding to a crack growth rate of 2.5 × 10−8 mm/cycle (10−9 in./cycle). In room temperature air environment, ΔKth was found to be 6.2 and 4.0 MPam (5.6 and 3.6 ksiin.) for R = 0.1 and R = 0.5, respectively. At the same ΔK level, crack growth rate was found to increase with increasing stress ratio. The influence of stress ratio on crack growth rate, however, decreases with increasing ΔK. By raising temperature to 93° C (200°F), ΔKth was found to be suppressed to 4.4 and 2.9 MPam (4.0 and 2.6 ksiin.) for R = 0.1 and R = 0.5, respectively. Stress ratio effect on crack growth rate is the same as at room temperature, but is less significant. Temperature was found to influence crack growth rate in the threshold region for both stress ratio studied, with higher crack growth rate at 93°C (200°F) than at room temperature. Temperature sensitivity was found to be less for R = 0.5 than R = 0.1. The existence of hydrogen was found to have little effect on ΔKth and low-rate fatigue crack growth behavior of this NiMoV rotor steel.

Fatigue Crack Growth Behavior of TA29 Titanium Alloy at Different Temperatures

2020 ◽  
Vol 993 ◽  
pp. 259-266
Author(s):  
Juan Li ◽  
Jian Ming Cai ◽  
Rui Duan ◽  
Xu Huang
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Steady State ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Room Temperature ◽  
Fracture Morphology ◽  
Rapid Expansion ◽  
State Expansion ◽  
Different Temperatures

TA29 titanium alloy forging was heated by duplex annealing. The fatigue crack growth behaviour of the alloy at room temperature, 400 °C, 500 °C and 600 °C was studied. The relationship between the fatigue crack growth rate (Da/dN) and the stress intensity factor amplitude (△K) of TA29 alloy at different temperatures was revealed by Paris formula. The fatigue fracture morphology of fatigue crack growth specimens was analysed by scanning electron microscopy (SEM). The results showed that the TA29 titanium exhibited good crack growth resistance at room temperature. With the increase of test temperature, the C value of the Paris formula increased, the m value decreased, and the fatigue crack growth rate increased. From the fatigue fracture morphology of the specimens, it was found that the fractures of fatigue crack growth specimens at different temperatures exhibited typical pre-splitting zone, steady-state expansion zone and rapid expansion zone. As the temperature increased, the range of the pre-cracking zone was larger, the range of the steady-state extension zone and the rapid expansion zone were smaller. At room temperature, there was no obvious fatigue strips in the steady-state expansion zone, and the transient fracture zone exhibited the characteristics of cleavage fracture, while the steady-state expansion zone at high temperature showed obvious fatigue strips and secondary cracks, and the transient fracture zone was a typical ductile fracture mechanism.

An Experimental Study for Low-Cycle Fatigue Crack Propagation of Glidcop Al-15

2017 ◽  
Vol 896 ◽  
pp. 128-133
Author(s):  
Yan Yin ◽  
Hai Bo Chen ◽  
Wei Ling Xiao
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Room Temperature ◽  
Stress Amplitude ◽  
Low Cycle Fatigue ◽  
Oxide Dispersion Strengthened ◽  
Cyclic Stress ◽  
Surface Cracks ◽  
Cycle Fatigue

Experiments have been conducted on an oxide dispersion strengthened (ODS) copper Glidcop Al-15 under a range of cyclic stress-amplitudes at room temperature. Special specimens containing an artificial small hole of various diameters, i.e. 150, 200 and 300 μm, were used. Propagation process of surface cracks in the various holed specimens was recorded to investigate the fatigue crack growth rate. Scanning electron microscope (SEM) was used for the observation of the fracture surface after failure specimens. The well-known Coffin-Manson low-cycle fatigue relationship was substantially shown through the results. An equation between the growth rate of the surface crack and the stress amplitude for Gidcop Al-15 was carried out. The experiment proved that prior fatigue history makes little influence on the subsequent crack propagation property under low-cycle condition.

Sign in / Sign up

Export Citation Format

Share Document