China 
Africa 
Explore chapters and articles related to this topic
Mechanical Properties of Materials in Microstructure Technology
Published in Bharat Bhushan, Handbook of Micro/Nano Tribology, 2020
Fredric Ericson, Jan-Åke Schweitz
Thermal fatigue is a special case of dynamic fatigue where the load cycling is caused by temperature changes and an associated variation in the thermal stress. The fatigue process is accelerated by the periodic temperature peaks, which causes thermal destabilization of the material, activates corrosion processes, speeds up diffusion processes, etc. Contrary to “normal” dynamic fatigue, which usually is of a high-cycle character, thermal fatigue often is of low-cycle character. Thermal chock is a well-known problem in brittle materials used for high-temperature applications. A rapid temperature change gives rise to a steep thermal gradient in the body, which fractures under the influence of the high local thermostress generated. Silicon and other conventional semiconductors are normally used in low-temperature applications and in chemically protected environments, and there is little reason to worry about thermal fatigue or thermal chock under these conditions. In the near future, however, materials like Si3N4 and SiC will be frequently used in micromachined structures for high-temperature applications, and phenomena such as thermal fatigue and thermal chock will have to be taken into consideration.
Integrated-Circuit Packaging
Published in Robert Doering, Yoshio Nishi, Handbook of Semiconductor Manufacturing Technology, 2017
Michael Lamson, Andreas Cangellaris, Erdogan Madenci
There exist many thermal fatigue life prediction models for determining the solder joint reliability of electronic packages, each with its own merits. These models are dependent on the package-level, statistical (empirical) failure parameters associated with a key parameter of the structure, such as viscoplastic strain energy or matrix creep strain calculated using FEA. The leading failure indicators for the correlation of thermal fatigue life are based on strain ranges such as the total, inelastic, and matrix creep strains (see Iannuzzelli et al. and Syed) [82,83] and the viscoplastic strain energy density increment by Darveaux [84]. One of the widely accepted failure criteria introduced by Darveaux [85] for thermal fatigue-life correlation is based on a relationship in terms of the volume-weighted-average inelastic work density increment. A complete description and application of this criterion to both the thermo-mechanical and mechanical bending fatigue life prediction is given by Madenci [87].
Fracture Morphology and Topography
Published in Colin R. Gagg, Forensic Engineering, 2020
As a failure mechanism, thermal fatigue will entail a gradual deterioration and eventual cracking of a material or component, simply by alternate heating and cooling cycles. During the course of thermal cycling, free thermal expansion (TE) of the component material may be partially or completely constrained. However, any constraint of TE will introduce thermal stresses, the level of which may eventually initiate and propagate a fatigue crack. As thermal fatigue cracking usually initiates below 50,000 cycles, it can be classified as a low-cycle fatigue mechanism. The following example will illustrate thermal fatigue cracking in action, where a lorry driver was seriously injured when the vehicle clutch exploded.
Effects of rare earth elements (Ce, La) on microstructure and mechanical properties in compacted graphite iron
Published in Philosophical Magazine, 2021
Jianan Zhu, Xintong Lian, Hengchang Lu, Qingyi Liu, Ailong Jiang, Duo Fang, Han Dong, Dexiang Xu
The engine cylinder head needs to be cooled down by water to ensure the normal operation of the diesel engine. For the purpose of simulating the actual working conditions, the thermal fatigue tester was used to test the thermal fatigue performance of CGI. With the beginning of the cold-heat cycle in the test, periodic alternating stress produced in samples causes thermal fatigue. The stress concentration and periodic thermal stress cause cracks to start from the preset notch, as shown in Figure 9. It has been reported that graphite is equivalent to a defect in cast iron and the graphite-matrix interface bonding strength is weak, the crack path usually extends along the graphite [17,20]. As shown in Figure 9(a)–(c), crack propagation direction is mainly along the vermicular graphite. It can be seen from the data in Table 5 that the length of the cracks decreased obviously with the percentage of vermicular graphite reduce. Generally, the crack lengths of RuT4 and RuT5 should be similar with the spheroidization of graphite. However, three main cracks propagated simultaneously in RuT5 matrix to release thermal stress, which is different from other samples with only one main crack, as shown in Figure 7(d). It is probably related to the existence of spheroidal graphite gathering towards preset V-shape notch. Therefore, the length and width of the crack are further reduced in RuT5. These findings can indicate spheroidal graphite have a stronger ability to resist crack propagation than vermicular graphite.
A comparative study on effects of thermal fatigue caused by thermal-oil cycling on tensile properties of single lap composite joints bonded with different kinds of adhesives
Published in The Journal of Adhesion, 2019
Tarkan Akderya, Onur Sayman, Uğur Kemiklioğlu, Oğuzhan Arap
Thermal cycling becomes a significant case when failure of PMCs by the alteration of mechanical properties is present. While thermal cycling is taking place, mechanical properties of the polymer matrix composites and epoxy-based adhesives are being affected by different parameters. When choosing an adhesive for a thermally demanding application, the chemical stability of the adhesives at high temperatures is one of the most important factors to consider. [3] Thus, a comprehensive experimental study is designed to find which parameter influences the mechanical properties at what rate. In this study, thermal fatigue process was applied to adhesively bonded glass fibre reinforced SLJs in order to investigate the effects of thermal fatigue on their tensile properties. Joints were subjected to thermal-oil cycling to achieve the thermal fatigue effect.
Mechanical properties of composite coating on cast iron by laser
Published in Surface Engineering, 2018
Pengyu Lin, Zhihui Zhang, Shuhua Kong, Hong Zhou, Xin Tong, Luquan Ren
Microhardness was examined using a Knoop and Vickers Hardness Table (USA), under the load of 25 g. Each value shown here is the average of six individual measurements. The MTS Hydraulic Servo Testing System (USA) was used for tensile tests. The tensile strain rate is 1 mm min−1. In addition, the thermal fatigue tests were carried out on a self-controlled thermal fatigue testing machine. A complete cycle consists of heating for 65 s at 700°C in resistance furnace, and then water cooling for 15 s at 20°C in a water tank. Plain-view and cross-sectional microstructures were characterised by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM, JSM-6700F, Japan) equipped with energy dispersive spectrometer (EDS) and high-resolution transmission electron microscopy (HRTEM, JEOL-2100F, Japan).