Thermal Fatigue Analysis Research Articles

Thermal Stress Analysis of Compact Heat Exchanger Produced by Additive Manufacturing

Abstract Compact heat exchangers are renowned for their high heat transfer rates and efficiency, achieved by incorporating mini and micro-channels in their core design. However, operating under conditions of high-pressure fluctuations and significant temperature differences between hot and cold streams can potentially induce fatigue failure. To the best of our knowledge, this study represents the first investigation into the thermal stresses experienced by heat exchanger samples manufactured by selective laser melting technology, focusing on circular channels. Experiments were conducted using hot water in the inner channel, while the remaining channels and the sample surface were subjected to natural convection in ambient air. Strain gauges, thermocouples, and RTDs were employed to measure strain and temperature variations over time. These data were utilized as inputs for a numerical model based on finite element method. The strain measurements were compared with those obtained from the numerical model, revealing an average difference of approximately 20%. Lastly, a thermal fatigue analysis based on the maximum equivalent stresses predicted by the numerical model is presented. The evaluation considered both S-N curves: outlined in the ASME standard and the one obtained with specimens produced through selective laser melting. In the case of circular channels manufactured through additive manufacturing evaluated in this work, thermal stresses alone are insufficient to cause component failure due to fatigue. However, significant pressure cycles superimposed on the model can reverse this situation, making the combined effect of thermal and mechanical stresses influential in determining the component's fatigue behavior.

Finite Element Analysis and Experimental Verification of Thermal Fatigue of W-PFM with Stacked Structure

As the prime candidate for plasma-facing materials (PFM), the response of tungsten (W) to thermal shock loads is an important research topic for future fusion devices. Under heat loads, the surface of tungsten plasma-facing materials (W-PFM) can experience thermal damage, including brittle cracking and fatigue cracks. Therefore, exploring solutions for thermal damage of W-PFM remains one of the current research focuses. We propose a novel approach to mitigate thermal radiation damage in PFM, namely, the stacked structure W-PFM. The surface thermal stress distribution of the stacked structure W-PFM under heat loads was simulated and analyzed by the finite element method. As the foil thickness decreases, both the peak thermal stresses in the normal direction (ND) and rolling direction (RD) decrease. When the thickness decreases to a certain value, the peak thermal stress in the RD decreases to about 1384 MPa and no longer decreases; while the peak thermal stress in the ND approaches 0 MPa and can be neglected. In the range of approximately 5–100 mm, the accumulated equivalent plastic strain decreases sharply as the thickness decreases; in other thickness ranges, it decreases slowly. Thermal fatigue experiments were conducted on the stacked structure W composed of W foils with different thicknesses and bulk W using an electron beam facility. The samples were applied with a power density of 30 MW/m2 for 10,000 and 20,000 pulses. The cracks on the surface of the stacked structure W extended along the ND direction, while on the surface of bulk W, besides the main crack in the ND direction, a crack network also formed. The experimental results were consistent with finite element simulations. When the pulse number was 10,000, as the thickness of the W foil decreased, the number and width of the cracks on the surface of the stacked structure W decreased. Only four small cracks were present on the surface of stacked structure W (0.05 mm). When the pulse number increased to 20,000, the plastic deformation and number of cracks on the surface of all samples increased. However, the stacked structure W (0.05 mm) only added one small crack and had the smallest surface roughness (Ra = 1.536 μm). Quantitative analysis of the fatigue cracks showed that the stacked structure W-PFM (0.05 mm) exhibited superior thermal fatigue performance.

Thermal fatigue analysis and structural optimization of sliding composite leaf spring

The thermal failure mechanism of sliding composite leaf springs (SCLSs) is examined in this research. Bench fatigue testing is used in the experimental investigation of the thermal failure temperature and mode. The findings demonstrate that after 20 min, when the temperature reaches the glass transition temperature, cracks start to form around the bolt hole of the composite body. The findings from bench experiments indicate that thermal fatigue failure of SCLS can be divided into three main forms: delamination failure of the resin-rich layer, the resin-fiber interface, and fibre pull-out failure. The utilization of finite element simulation has demonstrated that when subjected to thermal load, the leaf spring’s internal defects can lead to localized stress concentration. The structure of the spring end is optimized using the insulating panel scheme and the metal joint scheme. The thermal fatigue issue with SCLS is best addressed by the heat dissipation approach, according to bench tests.

Thermal fatigue analysis of district heating pipeline under variable frequency regulation of circulating water pump

The use of variable frequency control of circulating water pumps is an important energy-saving operation strategy to cope with changes in heating load. However, it can lead to low cycle fatigue failure of the pipeline when the cyclic stress generated by frequent water temperature fluctuations reaches the fatigue limit. Accurately prediction of the maximum total temperature difference cycles of pipelines is of great significance for ensuring the safe operation of centralized heating networks with frequent water flow rates regulation. Based on the actual operating data of 360,000 heat exchange stations, the stress amplitude and corresponding temperature difference cycles of pipelines at different operating temperatures were calculated, the maximum total temperature difference cycle of pipelines for 30 years was predicted. We calculated the stress limit of pipelines at different safety levels, and evaluated the impact of temperature on the fatigue life of pipelines under different building types and working conditions. The results show that the number of temperature difference cycles in primary network pipelines is three times that in secondary network pipelines, and the number of temperature difference cycles in pipelines of different building types varies greatly. The lower the operating temperature of the pipeline, the smaller the temperature difference fluctuation and the greater the contribution of pipeline fatigue damage when regulating the variable flow rate of the circulating water pump. The stress limit values of primary network supply and return water pipelines are 650 MPa and 759 MPa, while the stress limit values of secondary network supply and return water pipelines are 811 MPa and 946 MPa.

Non-axisymmetric Modeling of a Moving Heat Source for Thermal Stress and Fatigue Analysis of Railway Vehicle Disc Brakes

Railroad vehicles require the use of disc brakes for safety purposes, however, the brakes are susceptible to thermal stress, which ultimately shortens their lifespan. Hence, to accurately predict the life of railway disc brakes in thermal load simulations, the availability of a model that considers spatial and temporal variations of temperature and thermal stress is essential. A non-axisymmetric moving heat source model was successfully developed to address spatial temperature variations (Deressa and Ambie in Urban Rail Transit 8(3–4):198–216, 2022. 10.1007/s40864-022-00176-9), and this study aims to extend this model to predict thermal stress and fatigue life, and assess its effectiveness. The analysis includes braking time thermal analysis, cooling time thermal analysis, and structural analysis. Spatially varying temperature is incorporated into the structural analysis to calculate thermal stress and strain. A fracture mechanics-based fatigue life estimation method is applied to critical areas of the friction surface. The model is implemented on two braking conditions (service and emergency) and two disc geometries (actual and modified). The model successfully resolves spatial heat considerations by estimating maximum stress variations of up to 46 MPa along the disc circumference. Stress differences of 3 MPa and 6 MPa are observed between the leading and trailing edges of the pad trace during late and mid-braking times, respectively. Fatigue life results identify critical positions and directions for fatigue life initiation. Additionally, these results are in accord with previous observations available in the literature. The proposed model can be easily implemented in various sliding friction applications such as drum brakes, engine pistons/cylinders, and camshafts.

Thermal Fatigue Analysis of Portable Power Supply Container for Radar with Military Environmental Test Specification

Thermal Fatigue Analysis of Portable Power Supply Container for Radar with Military Environmental Test Specification

Thermal fatigue analysis of gold wire bonding solder joints in MEMS pressure sensors by thermal cycling tests

Thermal fatigue is one of the main causes of device failure in micro-electro-mechanical systems (MEMS). Gold wire bonding plays the role of electrical connection and signal transmission, which is the key structure of MEMS pressure sensor. In this paper, the fatigue failure of gold wire bonding solder joints caused by the thermal cycling test was studied. The thermal cycling test on MEMS pressure sensor was conducted using a temperature chamber with the cycling temperature range from −40 °C to 150 °C. After 1600 cycles, the solder joints were found with significant resistance increase to about 25 Ω or even overrange value by electrical measurement. In addition, the computed tomography (CT) scanning results showed that the solder joints on the substrate underwent thermal fatigue failure and one joint was separated from the pad with a distance of 36 μm, while the solder joints on the chip were still in good bonding conditions. The mechanism of thermal fatigue failure can be summarized as the thermal mismatch of solder joint materials, residual stress due to the bonding process, and stress concentration caused by the wedge area.

Thermal fatigue analysis of structures subjected to liquid metal jets at different temperatures in the Gen-IV nuclear energy system

In the Generation-IV (Gen-IV) nuclear reactor system, the liquid metal cooled fast reactor is regarded as a promising reactor type, especially the sodium-cooled fast reactor (SFR). It is necessary to investigate the thermal striping of liquid metal jets and the thermal fatigue behavior of adjacent structures at the core outlet of a liquid metal cooled fast reactor where coolant at different temperatures is mixed and causes thermal fatigue of adjacent structures. In this work, a fluid-structure coupling model and thermal fatigue assessment methodology are proposed and employed to study the thermal fatigue of structures subjected to liquid mental jets at the core outlet of the SFR. The temperature field and velocity distribution of the fluid, as well as the deformation and thermal stress of structures are obtained. The transient load and thermal fatigue damage of the structure at different locations are also calculated and analyzed. The fatigue damage factor of the structure is less than 1.0. The max deformation is predicted and a relatively large von Mises stress is located in the junction of central column and control rod guide tube, as well as the area of geometric structure mutation.

Investigation on Thermal Stress Analysis of Brake Disc Using ANSYS Simulation

The brake system is a basic and one of the most important systems of an automobile vehicle. Brake rotors of disc brakes rotate with the wheels, and brake pads, which are fitted to the brake calipers, clamp on these rotors to stop or decelerate the wheels. They convert the vehicles kinetic energy into heat, vibration, and sound energies, so that the vehicle can be brought to a halt. This change in energy occurs between the brake pads and the rotors or disc in a disc brake system. In this study we focus on the high thermal stresses endured by the disc during this energy conversion. Due to these stresses, the material used for the discs becomes a very important factor as we have to choose the right material which can make these discs efficient and more durable. In this research work, the Formula Student Vehicle disc has been chosen and simulation of the thermal stresses and fatigue analysis with different materials of stainless steels (SS) grades like SS 304, SS 410, SS 321, and SS 310 was carried. These materials were chosen as these are readily available and the cost of manufacturing of these discs will be reduced. By the use of Solidworks software, the disc is designed. With the help of Ansys workbench, the simulation of the thermal stress analysis and fatigue of the discs is done. From this research output, the stainless steels grade SS 410 had better results.

Conjugate Heat Transfer Analysis of the Aero-Thermal Impact of Different Feeding Geometries for Internal Cooling in Lifetime Extension Processes for Heavy-Duty Gas Turbines

Regulations from the European Union move towards a constant reduction of pollutant emissions to match the single-digit goal by 2050. Original equipment manufacturers propose newly designed components for the lifetime extension ofgGas turbines that both reduce emissions and allow for increasing thermodynamic performance by redesigning turbine cooling geometries and optimizing secondary air systems. The optimal design of internal cooling geometries allows for reducing both blade metal temperature and coolant mass-flow rates. In the present study, four different geometries of the region upstream from the blade’s internal cooling channels are investigated by using computational fluid dynamics with a conjugate heat transfer approach. The baseline configuration is compared to solutions that include turbulators, vanes, and a diffuser-like shapes. The impact of each solution on the blade metal temperature is thoroughly analysed. The diffuser-like solution allows for a more uniform distribution of the coolant and may reduce the metal temperature by 30% in the central part of the blade. There are also regions where the metal temperature increases up to 15%, thus requiring a specific thermal fatigue analysis. Eventually, the non-negligible impact of the coolant flow purged in the tip clearance region on the generation of the tip leakage vortex is described.

Thermal fatigue analysis of different nano coating thickness by air plasma spraying in diesel engine thermal barrier coating

Abstract The use of Atmospheric Plasma Spraying (APS) and yttria stabilized zirconia (YSZ) nanostructured coatings has been applied to the bond layer of NiCrAlY coated engine cylinder heads, pistons, and valve substrates. Thermal barrier coatings (TBCs) have been utilized to increase the engine performance in the design of combustion chamber components for internal combustion engines. ASTM-C-633-01 standard has been employed to conduct the bonding strength testing. It was also considered and directed to estimate the coating’s thermal performance by evaluating its insulation value and conducting a thermal insulation durability assessment. Field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD) were used to look at the nano powders and coatings’ microstructures and phase compositions. In YSZ, it was discovered that the topcoat of samples had a tri-modal pattern of nano sized particles engaged by the powder, micro-columnar grains generated from the re-solidification of the molten part of the powder, and almost equiaxed grains, which were a unique construction feature. The results demonstrated the creation of nano zones in one of three nanostructured coating zones and improved the top coating properties, including bonding strength and thermal insulation capacity. The high temperature of the diesel engine caused fatigue failure in the intake and exhaust valves.

Study on Thermal Stratification of Marine Reactor Surge Line Based on Operating Data

The thermal stratification of marine reactor surge line is divided into four types of typical transient based on the operating data: power increase, power decrease, off-design conditions, and small spray flow. The dimensionless Richardson number (Ri) analysis and the numerical simulation calculation of transient conditions are performed separately for these typical transients, generating the thermal stratification section length, duration and maximum temperature difference along the horizontal line section of the surge line under these typical transients. As indicated by the results, the thermal stratification under power increase and decrease transient conditions extends through the surge line just once, and the surge line safety may be affected by the circulating thermal fluctuation at the joint under the power increase transient condition, the thermal stratification of long section, long time and large temperature difference in the horizontal section under the small spray flow transient condition, and the thermal stress fluctuation caused by the off-design conditions. The method of study on thermal stratification of surge line based on operating data, proposed in this paper, lays a foundation for the subsequent thermal stress and thermal fatigue analyses, and also provides reference for the thermal stratification studies of other volumetric equipment.

Thermal fatigue analysis of Saffil reinforced aluminium alloys using pressure die casting process

ABSTRACT There are several constituents which causes die fractures in die casting process. Several features can be managed to a certain level by the help of specialists like geometry experts, production specialists and engineers. In die casting procedure main loading feature is fluctuating nature of thermal condition therefore effect of further forces comparatively negligible. In order to achieve cost-efficient manufacturing for die casting different metals essentiality of die’s high operational life is required. Expenditure on die substitution is very high and it increases manufacturing period. Failure of die can be recognised when there is fracture line appears on die surface and it grows during further manufacturing. The main objective of this work to find out thermal fatigue analysis of Saffil reinforced Aluminium Alloy (96%Al2O3 and 4% SiO2) dies during pressure die casting procedure. The location of cooling channels from base is varying (0.5 mm–5 mm). Thus six geometry models occurred for every material. Using ANSYS workbench 17.1 to find three major factors related to this analysis work temperature distribution, fatigue life and normal stresses generated in dies.

Effect of die geometry on thermal fatigue analysis of aluminium alloy (A02240) dies of low melting point alloys casting using pressure die casting process

ABSTRACT There are several constituents that cause die fractures in the die casting process. Several features can be managed to a certain level with the help of specialists like geometry experts, production specialists and engineers. In the die casting procedure, the main loading feature is the fluctuating nature of thermal conditions; therefore, the effect of further forces is comparatively negligible. In order to achieve cost-efficient manufacturing for die casting, different metals' essentiality of die’s high operational life is required. Expenditure on die substitution is very high and it increases the manufacturing period. Failure of die can be recognised when fracture line appears on the die surface and it grows during further manufacturing. The main objective of this work is to find out thermal fatigue analysis of aluminium alloy (A02240) dies during the pressure die casting procedure. The location of cooling channels from base is varying (0.5–5 mm). Thus, we get six geometry models for every material. By using ANSYS workbench 17.1, we find three major factors related to this analysis: work temperature distribution, fatigue life and normal stresses generated in dies.

Diurnal temperature variation as the source of the preferential direction of fractures on asteroids: Theoretical model for the case of Bennu

It has been shown that temperature cycles on airless bodies of our Solar System can cause damaging of surface materials. Nevertheless, propagation mechanisms in the case of space objects are still poorly understood. Present work combines a thermoelasticity model together with linear elastic fracture mechanics theory to predict fracture propagation in the presence of thermal gradients generated by diurnal temperature cycling and under conditions similar to those existing on the asteroid Bennu. The crack direction is computed using the maximal strain energy release rate criterion, which is implemented using finite elements and the so-called Gθ method (Uribe-Suárez et al. 2020. Eng. Fracture Mech. 227:106918). Using the implemented methodology, crack propagation direction for an initial crack tip in different positions and for different orientations is computed. It is found that cracks preferentially propagate in the North to South (N-S), in the North-East to South-West (NE-SW) and in the North-West to South-East (NW-SE) directions. Finally, thermal fatigue analysis was performed in order to estimate the crack growth rate. Computed value is in good agreement with available experimental evidence.

Innovative analytical model for temperature prediction of front-end accessory drive

The front-end accessory drive belt drive system is a critical component in the vehicle engine. To avoid thermal deterioration under static state operating conditions, the thermal distribution for the belt drive system at each condition must be determined in an efficient manner. Due to the numerical approach is not feasible to address this concern because of its high computational cost, this paper proposes a reliable and efficient novel analytical thermal model to achieve this goal. This work develops the state-of-the-art heat transfer ordinary differential equations (ODEs) describing the thermal flow and heat dissipations on the complex structures of pulleys. Then it integrates these ODEs with heat transfer governing equations of the belt and heat exchanges to establish an innovative system of equations that can be solved within a few seconds to provide temperature plots. Moreover, experiments were conducted on a dynamometer to verify the accuracy of the proposed model under a wide range of conditions. The results indicate that the measured temperatures are in good agreement with the corresponding analytical results. Owing to its efficiency, the proposed model can be integrated with other mechanical characterizations of the belt drive system in terms of design, optimization, and thermal fatigue analyses.

Temperature field analysis of fuel injection nozzle based on fluid-solid coupling method

Fuel injection nozzle is one of the key components of fuel injection system. The accuracy of the temperature field analysis is related to its working reliability. In order to obtain the temperature field of the nozzle, this paper considers the interaction of the fluid domain and solid domain, establishing a heat transfer model by fluid-solid coupling method. Compared with empirical formula method, the results show that the coupling method can fully simulate the characteristics of the flow fluid and improve precision of the temperature of the nozzle, which plays an important role in the subsequent thermal fatigue analysis of the nozzle.

Thermal Fatigue Analysis of the Secondary Network of District Heating Systems in China

AbstractCentral heating is the main heating method in cities in northern China in winter, and it is also an important part of urban utilities. The safety of the heating pipe network operation is an...

Impact monitoring characteristics of piezoelectric paint sensor by thermal fatigue analysis for railroad vehicle applications

The strong aerodynamic drag under a railroad vehicle in motion causes the track ballast to fly up and around. The flying ballast can collide with the underside of the coach, damaging the electronics installed there. There are even cases wherein the aerodynamics of fast-moving train causes the gravel to hit the side of the coach and break the windows. Extensive and numerous studies are underway to reduce the damage caused by such phenomena. In this study, a “smart paint sensor” for impact monitoring was fabricated using piezoelectric nano powder and commercial paint for railroad vehicles, and the application of impact monitoring to railroad vehicles was analyzed. The process was simplified because the use of commercial paint eliminated the need to apply an additional layer of functionalized paint. Furthermore, the fact that the paint can be evenly sprayed on a large surface made it suitable for use on large and intricate objects such as a railroad vehicle bogie. Because railroad vehicles are exposed to thermal stress for a long period of time, a thermal fatigue test was conducted in order to figure out the stability of the polymer-based material, which is relatively vulnerable to temperature variations. The test results were used to analyze the impact sensitivity of the piezoelectric paint sensor. For the analysis, a full-size mock-up of the railroad vehicle bogie and an impact monitoring system with piezoelectric paint sensor were implemented in order to visualize the impact signals from differently shaped objects with large surfaces.

Thermal fatigue analysis of H13 steel die adopted in pressure-die-casting process

The thermal fatigue of die casting die steels causes reduction in tool life and seriously affects the surface conditions such as microstructure, hardness, surface finish and residual stresses. The improvement of die life by suitably modifying the die design assumes utmost importance for die designers. In this regard, a key issue is the size and location of cooling channels relative to the surface of the die, which affect the thermal stresses and fatigue life of dies. This paper focuses on thermal fatigue analysis of pressure-die-casting die steel H13 and analyses the effect of coolant channel location on temperature distribution and fatigue parameters such as life, damage, equivalent alternating stress and biaxiality using ANSYS Workbench 15.0 finite-element package. Increase in wall thickness (location of coolant channel from base) caused an increase in temperature and decrease in die life, which led to increase in volume porosity and hence crack initiation. The optimum coolant channel location from the base is obtained as 1 mm, which corresponds to minimum normal stress of 149.1 MPa, fatigue life of 4.1 × 105 cycles, fatigue damage of 2436.9 and equivalent alternating stress of 100.62 MPa.