Authors: Xin Chun Shang, Yan Ting Xu, Pei Fei Wu
Abstract: The metal would overheat and even burn under the thermal shock arisen as laser drilling, which causes micro-damage inside the metal. Cavitation is the most important origin for crack propagation and failure of metal. To understand the damage mechanism in the heat affected zone of the high temperature nickel based superalloy DD6, an experiment of microvoid nucleation was designed and implemented by laser drilling in DD6 sheet. The complex characteristics of micro-damage including microvoid near the perforation were observed by scanning electron microscopy. An analytic solution of the temperature field in DD6 sheet for thermal shock arisen as laser drilling was obtained on the basis of the non-Fourier heat conduction theory. As a result, the minimum of peak temperature during the thermal shock in the zone of microvoid nucleation was estimated, it can be approximately regarded as critical temperature of nucleation.
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Abstract: Reliability failure analysis is extremely important in the manufacturing process of PCB (Printed Circuit Board). In this paper, we use thermal shock test method to analysis the electrical interconnection reliability of PCB in harsh environment. Also taking into account the reliability of PCB is closely related to its design and technology, approaches of technological improvement are proposed. Finally through temperature shock test method, the results show that the reliability of PCB designed with improved technology is enhanced.
391
Authors: Hong Jie Zeng, Lai Qi Zhang, Xin Yu He, You Cha Zhang, Pen Jia, Jun Pin Lin
Abstract: As a material intended for application in hot-dip galvanization, Ti28.15Al63.4Nb8.25Y (at %) coatings were deposited onto 316L stainless steel substrate using high velocity oxygen fuel (HVOF) and atmospheric plasma spray (APS), respectively. The influence of different thermal spraying techniques on the microstructure, phase transformation, porosity, bond strength and hardness values of Ti28.15Al63.4Nb8.25Y coatings was analyzed by scanning electron microscopy (SEM), X-ray diffraction, tensile test and other analysis methods. In addition, the thermal shock test of Ti28.15Al63.4Nb8.25Y coatings was carried out to evaluate the desquamation resistance and the model of invalidation. The results indicated that HVOF Ti28.15Al63.4Nb8.25Y coatings had more uniform and compact morphology than APS Ti28.15Al63.4Nb8.25Y coating and HVOF Ti28.15Al63.4Nb8.25Y coatings have lower porosity and oxide content. The coatings processed by HVOF had higher bond strength, microhardness and thermal shock resistance and displayed better mechanical properties than that prepared by APS.
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Authors: Long Quan Shao, Bin Deng, Yuan Fu Yi, Qi Liu, Wei Wei Zhang, Ning Wen
Abstract: In this study, the binding performance of a Cercon-based zirconia framework material and special Cercon Ceram S zirconia veneering porcelain is discussed. Rectangular 30 mm × 20 mm × 2 mm porcelain blocks were made from zirconia using the CAD/CAM system. The 2 mm veneering porcelain was then sintered onto blocks at a temperature of 850-800°C with a loading speed of l mm/min. The shear bond strength of the interface was tested. Sintering was studied by visual observation, scanning electron microscopy, energy dispersive spectroscopy (EDS), thermal shock test and other methods. Excellent sintering results of the zirconia framework material and veneering porcelain can be achieved. The cross-sectional morphology of the samples, observed by SEM, shows a uniform, fine, and smooth texture for the veneering porcelain, whereas that of the zirconia framework material shows a rough surface with a uniform and compact texture. EDS results indicate that a small amount of A12O3 and SiO2 is present in the zirconia area, and no ZrO2 or Y2O3 is detected in the veneering porcelain area. No interlayer radial crack or flaw is found throughout the entire thermal shock test of the samples at 60-240°C. Thus, the cracking temperature of the samples is pegged at T>240°C. The shear bond strength of the interface is 32.62±5.77 MPa. Chemical element infiltration exists between zirconia and the veneering porcelain, indicating the chemical bond between the two. An excellent match between the Cercon-based zirconia framework and the special veneering porcelain can be achieved, which can satisfy clinical requirements.
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Authors: Jun Cui, Jun Ou, Yong Lie Chao, Q.P. Gao, Guang Fu Yin, H. Wang, J.F. Shen, Yang Xi Chen
Abstract: Dental ceramic materials do not always show linear expansion behavior. In general, thermal
contraction behavior of dental porcelain can be described with the polynomial function: L/L= C+α1
T+α2 T2. In addition, a new method for taking into consideration of nonlinear contraction behavior of
dental ceramics is proposed for calculating thermal mismatch value (α) between substrate and
veneering materials. Discs of eight substrate/veneer combinations (n=10) were fabricated for thermal
shock testing. In this study, a stepwise multiple regression analysis was performed to determine the
relationship between thermal shock test results and thermal mismatch value (α) on these
combinations. A high degree of correlation was found between αs-b and T. The new method proves
to be a reliable one to predict thermal compatibility of multi-layer dental ceramic composites.
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Authors: Samson Yoon, Seung Min Cho, Yuri Lee, Bong Tae Han
Abstract: A unique interferometric system utilizing thermal-conduction loading is developed and
implemented to investigate the effect of ramp rates of accelerated test profiles on the thermal
deformation of flex package assemblies. The system provides extreme ramp rates to simulate the
thermal shock condition with a temperature control much finer than the conventional convection
based system can provide. The in-plane and out-of-plane displacements of the flex package are
documented through moiré interferometry and Twyman/Green interferometry, respectively.
Deformation measured under a thermal shock condition is compared with that under the
conventional thermal cycling condition to assess the effect of ramp rates on package deformation.
The comparison reveals that a low ramp rate of typical accelerated thermal cycling (ATC) tests
causes significant reduction in the maximum level of elastic energy in the package assembly.
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Authors: Sawao Honda, Hiroaki Tanaka, Hideo Awaji
Abstract: Thermal shock is a mechanism often leading to failure of ceramic materials that may occur
during rapid heating or cooling. These tests were performed in order to compare the thermal shock
resistance of ceramic materials by cooling with that of the heating method and hence to evaluate
parameters such as thermal shock strength (R1c) and thermal shock fracture toughness (R2c).
During the present study, thermal shock resistance of alumina and mullite ceramics was estimated
experimentally and theoretically using the thermal shock parameters. The critical thermal stress at the
onset of thermal shock fracture was calculated using fracture time, which is measured by an acoustic
emission. Results show that thermal shock parameters of alumina specimens decreased with
increasing temperature of fracture point. This effect can be attributed to the temperature dependence
of the thermal properties. The experimental values of thermal shock parameters evaluated by IRH
and WFC techniques were in good agreement at the temperature of fracture point. The thermal shock
parameters enabled the definition of a unified thermal shock resistance of ceramics, which is
independent of the nature of the testing techniques.
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Authors: Cheng Ji Xian, Hideo Awaji
Abstract: Thermal shock test for porous SiC ceramics heated up to testing temperature was
performed by a water flow cooling method. In order to find the influence of the penetration for the
porous material under the thermal shock, transient temperature distribution was simulated with taking
account of the infiltration of the cooling media into the specimen. Thermal stress distributions in the
specimens were also calculated from the estimated temperature distributions. In this study, it was
evident that the temperature variation of the porous ceramics was more rapid than that of the ceramics
without taking account of the penetration.
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