Temperature Dependence of Density and Thermal Expansion of Wrought Aluminum Alloys 7041, 7075 and 7095 by Gamma Ray Attenuation Method

Narender, K.; Rao, A. S. Madhusudhan; Rao, K. Gopal Kishan; Krishna, N. Gopi

doi:10.4236/jmp.2013.43045

Cited by 19 publications

(4 citation statements)

References 20 publications

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“…The range for power in the experimental plan has been decided so that the specific threshold irradiance for conduction to key-hole transition would be overcome. Sensible values for welding speed have been found via preliminary trials in the form of bead-on-plate tests aiming at producing full penetration with no significant dropthrough on the lower surface, thus matching the requirements as defined in the referred standard [11].…”

Section: Methodsmentioning

confidence: 92%

Semi-Analytical Solution for Modelling Moving Heat Sources in a Semi-Infinite Medium with Radiative and Convective Boundary Conditions

Metallo

2023

International Journal of Thermodynamics

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The weld quality is highly related to the thermal history of the weld and there have been many trials to monitor the quality using an infrared (IR) sensor. To obtain the real temperature of a surface based on the brightness temperature values measured by an IR camera, the emissivity value must be derived. For an accurate assessment of the emissivity, one must be aware of the melting point isotherm. The temperature profiles only depend on three factors during laser processing, specified as constants the characteristics of the material: laser beam speed (v), laser beam diameter (d), and power (P). Predicting the width of the melted zone reached during the welding process as the parameters vary is a tool for helping a quality laser processing and for determination of true temperature in laser welding using IR camera. This study describes the semi-analytical (SA) solution of the heat conduction equation for a localized moving Gaussian heat source with constant parameters on a semi-infinite medium. The solution, simple and quick to obtain, provides information on the width of the melted zone with an average error < 5 %. The outcome is assessed numerically and contrasted with FEM solutions for a Gaussian source, the latter having undergone experimental validation. With two distinct defocus values, def0 and def-6, and by varying the speed and power settings, two separate types of experiments were run. Thus, the SA solution was obtained and compared after the FEM solution had been obtained with a good approximation (max err 4.3 %, average err 2.7 %). Only in regard to the 1AL test is an error more than 5 % detected; in the other case, the average error is 3.75 %. Two more tests at the defocus values of def-4 and def-8 were conducted to confirm the model's validity as the parameters varied. Overall, the average error between the semi-analytical and the FEM solution is 4.1%. The SA solution may be used to effectively estimate the isotherms related to the melting point of aluminum (770 K). This allows to obtain a tool which helps restoring the real temperature based on the brightness values measured by the IR camera during laser welding. At the same time, this effective tool allows to investigate the importance of different processing parameters in laser manufacturing.

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Section: Methodsmentioning

confidence: 92%

Semi-Analytical Solution for Modelling Moving Heat Sources in a Semi-Infinite Medium with Radiative and Convective Boundary Conditions

Metallo

2023

International Journal of Thermodynamics

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“…Materials' Properties: Since the proposed model considers the solid-liquid phase change, the properties at ambient temperature for the solid phase and at melting temperature for the liquid phase were used. Specific heat, thermal conductivity coefficient [18,22], and density [11,19] were then defined (Table 4). The absorption value was chosen for aluminum 0.16 [20,21].…”

Section: Numerical Modeling: Finite Element Methodsmentioning

confidence: 99%

Emissivity Prediction for an IR Camera During Laser Welding of Aluminum

Metallo

2022

International Journal of Thermodynamics

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Laser processing is becoming increasingly important in industrial applications. The success of the process relies on two fundamental parameters: the surface temperature of the medium and the thickness of the hardened layer. One of the most important factors during a laser process is certainly the temperature, which presents high temperature gradients. The speed at which a material undergoes a phase transition, the chemical reactions that take place during processing and the properties of the material are all dependent on temperature changes. Consequently, the measure of temperature is a demanding undertaking. This study proposes to measure temperature for the duration of laser welding with the infrared camera (IR) Optris PI. To restore the real temperature based on the brightness temperature values measured by the IR camera is needed to evaluate the emissivity to be attributed to the IR camera. For this purpose, firstly, the isotherms consistent with the melting point of aluminum (785 K) were assessed and then compared with the temperature distribution gauged in the zone of irradiation of the laser. Such data were then compared with the thickness of the melted zone. The use of the melting point isotherm allowed the calculation of the value of emissivity and the restoration of the temperature. Thermography software data acquisition wrongly presupposes the emissivity value does not change. This generates incorrect thermographic data. The surface emissivity normally hinges on temperature. Therefore, the values on which the literature relies may not work for materials of interest in the conditions of the process. This is particularly the case, where welding is carried out in keyhole mode (Tmax = Tvap). However, the physical phenomena involved, including evaporation and plasma plume formation, high spatial and temporal temperature gradients, and non-equilibrium phase transformations, influence the optical conditions of the brightness of the emission of light from the molten pool, making, De Facto, the emissivity value not constant. Thus, what we propose here is a methodological procedure that allows the measurement of the effective emissivity of the surface, at the same time taking into consideration the consequence of physical phenomena and the conditions of the surface. Two procedures (Standard and Simplified) capable of providing the correct emissivity value in relation to the working parameters have been proposed. The results showed that the procedures are correct, fast, and easy to use.

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“… ( a ) Modulus of elasticity [ 29 ] and ( b ) density [ 30 ] of the aluminum beam at different temperature. …”

Section: Figurementioning

confidence: 99%

Temperature Compensation for Reusable Piezo Configuration for Condition Monitoring of Metallic Structures: EMI Approach

Baral

Negi

Adhikari

et al. 2023

Sensors

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This paper presents a novel algorithm for compensating the changes in conductance signatures of a piezo sensor due to the temperature variation employed in condition monitoring using the electro-mechanical impedance (EMI) approach. It is crucial to consider the changes in an EMI signature due to temperature before using it for comparison with the baseline signature. The shifts in the signature due to temperature can be misinterpreted as damages to the structure, which might also result in a false alarm. In the present study, the compensation values are calculated based on experiments on piezo sensors both in a free boundary condition and in a bonded condition on a metallic host structure. The values were further validated experimentally for damage detection on a large 2D steel plate structure. The variation in first natural frequency values for the unbonded piezo sensor at different temperatures has been used to develop the compensation algorithms. Whereas, in the case of the bonded sensor, the shift in structural peaks has been used. The developed compensation relations showed promising results in damage detection. Lastly, a finite element-based study has also been performed, supporting the experimental findings. The outcome of this study will aid in the compensation of the signatures in the structure due to temperature variation in the conductance signature.

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Temperature Dependence of Density and Thermal Expansion of Wrought Aluminum Alloys 7041, 7075 and 7095 by Gamma Ray Attenuation Method

Cited by 19 publications

References 20 publications

Semi-Analytical Solution for Modelling Moving Heat Sources in a Semi-Infinite Medium with Radiative and Convective Boundary Conditions

Semi-Analytical Solution for Modelling Moving Heat Sources in a Semi-Infinite Medium with Radiative and Convective Boundary Conditions

Emissivity Prediction for an IR Camera During Laser Welding of Aluminum

Temperature Compensation for Reusable Piezo Configuration for Condition Monitoring of Metallic Structures: EMI Approach

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