scholarly journals Design and Development of a Micro-LDH Apparatus to Determine Formability of Sheet Metal Under Hot Stamping Conditions Using Gleeble

2021 ◽  
Author(s):  
Amarjeet Kumar Singh ◽  
Krishnaiyengar Narasimhan
Keyword(s):  
Temperature Distribution ◽  
Hot Stamping ◽  
Thermomechanical Analysis ◽  
Uniform Strain ◽  
Forming Limit ◽  
Uniform Temperature ◽  
Electrical Cable ◽  
Uniform Temperature Distribution ◽  
Experimental Apparatus ◽  
Strain Paths

Abstract In the last few years, demand for hot stamped components has increased in the automotive industry. Determination of formability under hot stamping is challenging due to elevated temperature, fast cooling and high punch velocity. Although there was various strive for formability determination but had limitations with experiments like non-uniform heating of specimen, non-uniform strain and temperature distribution. Therefore, in this work, an experimental apparatus was developed to determine formability at room temperature, high temperature, hot stamping conditions, and any complex process cycle involving heating and cooling. New specimen was designed to produce different strain paths, uniform and homogenous temperature distribution with the help of FEM software using thermomechanical and thermoelectrical simulation. A micro hemispherical dome based experimental apparatus was designed using Solidworks. The designed apparatus was used in conjunction with the thermo-mechanical simulator (Gleeble-3800). Thermomechanical analysis was done in PAM STAMP software to optimize specimen size and shape to get uniform strain distribution and different strain paths. A thermoelectric FEM model was developed using Abaqus 6.14 to optimize the temperature distribution in the specimen. The developed model enables choosing the appropriate polarity of the electrical cable connection to achieve uniform temperature distribution in the specimen. Strain path and temperature profiles for experiment and simulation were compared. Further, a forming limit curve was developed using the designed apparatus to verify the feasibility of the apparatus. For feasibility test of apparatus, hot stamping process was selected. This new design apparatus can be used for a range of temperatures up to 1000 °C, hot stamping conditions, and for different materials (aluminium, magnesium alloys, different grade of steel, etc.). It concludes that the connection of different polarities of electrical cable was critical for homogenous and uniform temperature distribution in specimens.

Non-uniform temperature distribution of the main reflector of a large radio telescope under solar radiation

2021 ◽  
Vol 21 (11) ◽  
pp. 293
Author(s):  
Shan-Xiang Wei ◽  
De-Qing Kong ◽  
Qi-Ming Wang
Keyword(s):  
Temperature Field ◽  
Temperature Distribution ◽  
Solar Radiation ◽  
Radio Telescope ◽  
Thermal Imaging ◽  
Uniform Temperature ◽  
Large Radio Telescope ◽  
Uniform Temperature Distribution ◽  
Uniform Temperature Field ◽  
Main Reflector

Abstract The non-uniform temperature distribution of the main reflector of a large radio telescope may cause serious deformation of the main reflector, which will dramatically reduce the aperture efficiency of a radio telescope. To study the non-uniform temperature field of the main reflector of a large radio telescope, numerical calculations including thermal environment factors, the coefficients on convection and radiation, and the shadow boundary of the main reflector are first discussed. In addition, the shadow coverage and the non-uniform temperature field of the main reflector of a 70-m radio telescope under solar radiation are simulated by finite element analysis. The simulation results show that the temperature distribution of the main reflector under solar radiation is very uneven, and the maximum of the root mean square temperature is 12.3°C. To verify the simulation results, an optical camera and a thermal imaging camera are used to measure the shadow coverage and the non-uniform temperature distribution of the main reflector on a clear day. At the same time, some temperature sensors are used to measure the temperature at some points close to the main reflector on the backup structure. It has been verified that the simulation and measurement results of the shadow coverage on the main reflector are in good agreement, and the cosine similarity between the simulation and the measurement is above 90%. Despite the inevitable thermal imaging errors caused by large viewing angles, the simulated temperature field is similar to the measured temperature distribution of the main reflector to a large extent. The temperature trend measured at the test points on the backup structure close to the main reflector without direct solar radiation is consistent with the simulated temperature trend of the corresponding points on the main reflector with the solar radiation. It is credible to calculate the temperature field of the main reflector through the finite element method. This work can provide valuable references for studying the thermal deformation and the surface accuracy of the main reflector of a large radio telescope.

Embedded resistive heating in composite scarf repairs

2016 ◽  
Vol 51 (18) ◽  
pp. 2575-2583 ◽  
Author(s):  
Mahdi Ashrafi ◽  
Brandon P Smith ◽  
Santosh Devasia ◽  
Mark E Tuttle
Keyword(s):  
Temperature Distribution ◽  
Outer Surface ◽  
Thermal Gradient ◽  
Thermal Damage ◽  
Electrical Current ◽  
Tensile Tests ◽  
Resistance Heating ◽  
Uniform Temperature ◽  
Uniform Temperature Distribution ◽  
Bond Strengths

Composite scarf repairs were cured using heat generated by passing an electrical current through a woven graphite-epoxy prepreg embedded in the bondline. Resistance heating using the embedded prepreg resulted in a more uniform temperature distribution in the bondline while preventing any potential thermal damage to the surface of the scarf repairs. In contrast, conventional surface heating methods such as heat blankets or heat lamps lead to large through thickness thermal gradient that causes non-uniform temperature in the bondline and overheating the outer surface adjacent to the heater. Composite scarf repair specimens were created using the proposed embedded heating approach and through the use of a heat blanket for circular and rectangular scarf configurations. Tensile tests were performed for rectangular scarf specimens, and it was shown that the bond strengths of all specimens were found to be comparable. The proposed embedded curing technique results in bond strengths that equal or exceed those achieved with external heating and avoids overheating the surface of the scarf repairs.

scholarly journals Enhancement of Exit Flow Uniformity by Modifying the Shape of a Gas Torch to Obtain a Uniform Temperature Distribution on a Steel Plate during Preheating

2018 ◽  
Vol 8 (11) ◽  
pp. 2197
Author(s):  
Thien Ngo ◽  
Junho Go ◽  
Tianjun Zhou ◽  
Hap Nguyen ◽  
Geun Lee
Keyword(s):  
Temperature Distribution ◽  
Temperature Difference ◽  
Steel Plate ◽  
Flow Distribution ◽  
Uniform Temperature ◽  
Flow Uniformity ◽  
Modified Model ◽  
Uniform Temperature Distribution ◽  
Basic Model ◽  
New Models

The objective of this study is to improve the exit flow uniformity of a gas torch with multiple exit holes for effective heating of a steel plate. The torch was simulated, and combustion experiments were performed for validation. Based on a basic model, three different revised models were designed and analyzed with the software ANSYS FLUENT 18.2. The flow uniformity (γ) of the velocity distribution at the multiple exit holes was investigated with the pressure drop ranging from 100 to 500 Pa. The basic model had flow uniformity ranging from 0.849 to 0.852, but the three new models had γ1 = 0.901–0.912, γ2 = 0.902–0.911, and γ3 = 0.901–0.914, respectively. The maximum percentage difference of the flow uniformity index between the three new models and the basic model was 7.3%. The basic model with nonuniform flow distribution made a temperature difference of the back side of the steel plate from the center to the edge of around 229 °C, while the modified model with uniform flow distribution had a smaller temperature difference of 90 °C. The simulation results showed good agreement with our experimental results for both the basic model and the modified model. The modified gas torch made a wider and more uniform temperature distribution on a preheated steel plate than the basic one. The results revealed that a trade-off between cost and flow uniformity, as well as the new gas torch, could be applied to a steel-plate preheating process before welding.

Toward Intelligent Online Scan Sequence Optimization for Uniform Temperature Distribution in LPBF Additive Manufacturing

2021 ◽  
Author(s):  
Keval S. Ramani ◽  
Ehsan Malekipour ◽  
Chinedum E. Okwudire
Keyword(s):  
Additive Manufacturing ◽  
Temperature Distribution ◽  
Laser Scanning ◽  
Open Architecture ◽  
Uniform Temperature ◽  
Computationally Efficient ◽  
Optimal Sequence ◽  
Sequence Optimization ◽  
Uniform Temperature Distribution ◽  
Scan Pattern

Abstract Laser powder bed fusion (LPBF) is an increasingly popular approach for additive manufacturing (AM) of metals. However, parts produced by LPBF are prone to residual stresses, deformations, and other defects linked to nonuniform temperature distribution during the process. Several works have highlighted the important role (laser) scanning strategies, including laser power, scan speed, scan pattern and scan sequence, play in achieving uniform temperature distribution in LPBF. However, scan sequence continues to be determined offline based on trial-and-error or heuristics, which are neither optimal nor generalizable. To address these weaknesses, we present a framework for intelligent online scan sequence optimization to achieve uniform temperature distribution in LPBF. The framework involves the use of physics-based models for online optimization of scan sequence, while data acquired from in-situ thermal sensors provide correction or calibration of the models. The proposed framework depends on having: (1) LPBF machines capable of adjusting scan sequence in real-time; and (2) accurate and computationally efficient models and optimization approaches that can be efficiently executed online. The first challenge is addressed via a commercially available open-architecture LPBF machine. As a preliminary step towards tackling the second challenge, an analytical model is explored for determining the optimal sequence for scanning patterns in LPBF. The model is found to be deficient but provides useful insights into future work in this direction.

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