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In Part 1, background information on mechanical properties and metallurgy of solder alloys and soldered joints has been presented. In Part 2, mechanisms of damage and degradation of components and soldered joints during soldering, transport and field life have been discussed, the most important mechanism being low cycle fatigue of the solder metal. In this third part, the determination of the fatigue life expectancy of soldered joints is discussed. Accelerated testing of fatigue is needed, as the possibilities of calculations are strongly limited. A temperature cycle test under specified conditions is proposed as a standard. A model is worked out for the determination of the acceleration factor of this test. A compilation of a number of solder fatigue test results, generated in the author's company, is presented.

The purpose of this study is to clarify the mechanism of ambient and transient temperature effects on piezoelectric pressure sensors, and to propose corresponding compensation measures. The temperature of the explosion field has a significant influence on the piezoelectric sensor used to measure the shock wave pressure. For accurate shock wave pressure measurement, based on the actual piezoelectric pressure sensors used in the explosion field, the effects of ambient and transient temperatures on the sensor should be studied.

The compensation method of the ambient temperature is discussed according to the sensor size and material. The theoretical analysis method of the transient temperature is proposed. For the transient temperature conduction problem of the sensor, the finite element simulation method of structure-temperature coupling is used to solve the temperature distribution of the sensor and the change in the contact force on the quartz crystal surface under the step and triangle temperatures. The simulation results are highly consistent with the theory.

Based on the analysis results, a transient temperature control method is proposed, in which 0.5 mm thick lubricating silicone grease is applied to the sensor diaphragm, and 0.2 mm thick fiberglass cloth is wrapped around the sensor side. Simulation experiments are carried out to verify the feasibility of the control method, and the results show that the control method effectively suppresses the output of the thermal parasitic.

The above thermal protection methods can effectively improve the measurement accuracy of shock wave pressure and provide technical support for the evaluation of the power of explosion damage.

The purpose of this paper is to provide a new three dimension physically based model to calculate the initial stress in silicon germanium (SiGe) film due to thermal mismatch after deposition. We should note that there are many other sources of initial stress in SiGe films or in the substrate. Here, the author is focussing only on how to model the initial stress arising from thermal mismatch in SiGe film. The author uses this initial stress to calculate numerically the resulting extrinsic stress distribution in a nanoscale PMOS transistor. This extrinsic stress is used by industrials and manufacturers as Intel or IBM to boost the performances of the nanoscale PMOS and NMOS transistors. It is now admitted that compressive stress enhances the mobility of holes and tensile stress enhances the mobility of electrons in the channel.

During thermal processing, thin film materials like polysilicon, silicon nitride, silicon dioxide, or SiGe expand or contract at different rates compared to the silicon substrate according to their thermal expansion coefficients. The author defines the thermal expansion coefficient as the rate of change of strain with respect to temperature.

Several numerical experiments have been used for different temperatures ranging from 30 to 1,000°C. These experiments did show that the temperature affects strongly the extrinsic stress in the channel of a 45 nm PMOS transistor. On the other hand, the author has compared the extrinsic stress due to lattice mismatch with the extrinsic stress due to thermal mismatch. The author found that these two types of stress have the same order (see the numerical results on Figures 4 and 12). And, these are great findings for semiconductor industry.

Front-end process induced extrinsic stress is used by manufacturers of nanoscale transistors as the new scaling vector for the 90 nm node technology and below. The extrinsic stress has the advantage of improving the performances of PMOSFETs and NMOSFETs transistors by enhancing mobility. This mobility enhancement fundamentally results from alteration of electronic band structure of silicon due to extrinsic stress. Then, the results are of great importance to manufacturers and industrials. The evidence is that these results show that the extrinsic stress in the channel depends also on the thermal mismatch between materials and not only on the material mismatch.

The model the author is proposing to calculate the initial stress due to thermal mismatch is novel and original. The author validated the values of the initial stress with those obtained by experiments in Al-Bayati et al. (2005). Using the uniaxial stress generation technique of Intel (see Figure 2). Al-Bayati et al. (2005) found experimentally that for 17 percent germanium concentration, a compressive initial stress of 1.4 GPa is generated inside the SiGe layer.

Selective laser melting (SLM) is a promising additive manufacturing technology in the field of complex parts’ fabrication. High temperature gradient and residual stress are vital problems for the development of SLM technology. The purpose of this paper is to investigate the influence of substrate characteristics on the residual stress of SLMed Inconel 718 (IN718).

The SLMed IN718 samples were fabricated on the substrates with different characteristics, including pre-compression stress, materials and pre-heating. The residual stress at the center of the top surface was measured and compared through Vickers micro-indentation.

The results indicate that the residual stress reduces when the substrate contains pre-compression stress before the SLM process starts. Both substrate thermal expansion coefficient and thermal conductivity affect the residual stress. In addition to reducing the difference of thermal expansion coefficient between the substrate and the deposited material, the substrate with low thermal conductivity can also decrease the residual stress. Substrate pre-heating at 150°C reduces nearly 42.6 per cent residual stress because of the reduction of the temperature gradient.

The influence of substrate characteristics on the residual stress has been studied. The investigation results can help to control the residual stress generated in SLM processing.

UNDER steady load conditions, materials in gas turbines are subject to various forms of static and alternating stresses. Changes in the operating conditions such as starting, load variations and shut down cause additional thermal stresses which limit the permissible rate of these changes in service. In stationary plants these effects can be minimized by adjustment of the starting and shut down procedure or by protection of the sensitive parts with a cooling flow. In gas turbines for propulsion purposes load changes are governed by external conditions, are more frequent and take place at a higher rate. The consequent thermal stresses are then referred to as thermal shocks. Various methods for testing the resistance of materials to thermal shocks have already been suggested and applied. However, they differ very widely, and no quantitative, or even comparable figures are available as yet.

Alloy 42 and, similarly, Kovar were developed to provide metallic feed‐throughs from the interior of ceramic components to the exterior. The low coefficient of thermal expansion (CTE) of ceramic needs to be almost matched by the feed‐through metal to allow reliable hermetically sealed connections. For this purpose these alloys have served very well. However, because of its wide‐spread use for military applications, for which component hermeticity has been required, as well as because of the easier attachment of low‐CTE die to low‐CTE lead frames, Alloy 42 has found its way into plastic components with often disastrous results. When surface mount solder joints connect materials with different CTEs, global thermal expansion mismatches result. Also, if the materials to which the solder bonds have CTEs that differ from the CTE of solder, local thermal expansion mismatches result. These thermal expansion mismatches are the cause of most SM solder joint failures. Alloy 42 and Kovar not only cause significant global and local thermal expansion mismatches, but are inherently more difficult to solder because of the low solubility of nickel and iron, the main constituents of these alloys, in tin. Pull tests of solder joints show that under the best of circumstances a solder joint that includes an Alloy 42 or Kovar surface is only half as strong as one made to copper surfaces.

The purpose of this paper is to present an upscale theory of the thermal-mechanical coupling particle simulation for non-isothermal problems in two-dimensional quasi-static system, under which a small length-scale particle model can exactly reproduce the same mechanical and thermal results with that of a large length-scale one.

The objective is achieved by extending the upscale theory of particle simulation for two-dimensional quasi-static problems from an isothermal system to a non-isothermal one.

Five similarity criteria, namely geometric, material (mechanical and thermal) properties, gravity acceleration, (mechanical and thermal) time steps, thermal initial and boundary conditions (Dirichlet/Neumann boundary conditions), under which a small-length-scale particle model can exactly reproduce both the mechanical and thermal behavior with that of a large length-scale model for non-isothermal problems in a two-dimensional quasi-static system are proposed. Furthermore, to test the proposed upscale theory, two typical examples subjected to different thermal boundary conditions are simulated using two particle models of different length scale.

The paper provides some important theoretical guidances to modeling thermal-mechanical coupled problems at both the engineering length scale (i.e. the meter scale) and the geological length scale (i.e. the kilometer scale) using the particle simulation method directly. The related simulation results from two typical examples of significantly different length scales (i.e. a meter scale and a kilometer scale) have demonstrated the usefulness and correctness of the proposed upscale theory for simulating non-isothermal problems in two-dimensional quasi-static system.

The purpose of this paper is to study the thermal behaviour of a fully wet porous fin of longitudinal profile. The significance of radiative and convective heat transfer has been scrutinised along with the simultaneous variation of surface emissivity, heat transfer coefficient and thermal conductivity with temperature. The emissivity of the surface and the thermal conductivity are considered as linear functions of the local temperature between fin and the ambient. Darcy’s model was considered to formulate the heat transfer equation. According to this, the porous fin permits the flow to penetrate through it and solid–fluid interaction occurs.

Runge–Kutta–Fehlberg fourth–fifth-order method has been used to solve the reduced non-dimensionalized ordinary differential equation involving highly nonlinear terms.

The impact of pertinent parameters, such as convective parameter, radiative parameter, conductivity parameter, emissivity parameter, wet porous parameter, etc., on the temperature profiles were elaborated mathematically with the plotted graphs. The heat transfer from the fin enhances with the rise in convective parameter.

The wet nature of the fin enhances heat transfer and in many practical applications the parameters, such as thermal conductivity, heat transfer coefficient as well as surface emissivity, vary with temperature. Hence, the main objective of the current study is to depict the significance of simultaneous variation in surface emissivity, heat transfer coefficient and thermal conductivity with respect to temperature under natural convection and radiation condition in a totally wetted longitudinal porous fin.

This study aims to investigate numerically a thermomechanical behavior of disc brake using ANSYS 11.0 which applies the finite element method (FEM) to solve the transient thermal analysis and the static structural sequentially with the coupled method. Computational fluid dynamics analysis will help the authors in the calculation of the values of the heat transfer (h) that will be exploited in the transient evolution of the brake disc temperatures. Finally, the model resolution allows the authors to visualize other important results of this research such as the deformations and the Von Mises stress on the disc, as well as the contact pressure of the brake pads.

A transient finite element analysis (FEA) model was developed to calculate the temperature distribution of the brake rotor with respect to time. A steady-state CFD model was created to obtain convective heat transfer coefficients (HTC) that were used in the FE model. Because HTCs are dependent on temperature, it was necessary to couple the CFD and FEA solutions. A comparison was made between the temperature of full and ventilated brake disc showing the importance of cooling mode in the design of automobile discs.

These results are quite in good agreement with those found in reality in the brake discs in service and those that may be encountered before in literature research investigations of which these will be very useful for engineers and in the design field in the vehicle brake system industry. These are then compared to experimental results obtained from literatures that measured ventilated discs surface temperatures to validate the accuracy of the results from this simulation model.

The novelty of the work is the application of the FEM to solve the thermomechanical problem in which the results of this analysis are in accordance with the realized and in the current life of the braking phenomenon and in the brake discs in service thus with the thermal gradients and the phenomena of damage observed on used discs brake.

Polymeric coatings and packaging are often used to enhance the temperature sensitivity of fiber Bragg grating temperature sensors. The high thermal expansion coefficient of the polymer enhances the thermal sensitivity by improving the wavelength shift due to thermal expansion. The adhesion of the polymeric coatings to the silica based optical fiber plays an important role in the wavelength response characteristics of fiber Bragg gratings with respect to temperature. Experiments are done to qualitatively analyze the influence of adhesion. Three‐dimensional finite element simulations have been carried out. Spring elements are used to interconnect the nodes of the meshed models of optical fiber and coating. The effect of adhesion is studied as a function of spring stiffness.