FE Simulation of Laser Assisted Bending

2005 ◽  
Vol 6-8 ◽  
pp. 745-752 ◽  
Author(s):  
M. Pitz ◽  
Marion Merklein
Keyword(s):  
Structural Changes ◽  
Local Heating ◽  
High Surface ◽  
Cutting Tools ◽  
Conventional Heating ◽  
Roll Forming ◽  
Heating Rates ◽  
Heating And Cooling ◽  
Steel Grades ◽  
Multi Phase

Steel has a long tradition and is used in nearly every application. In order to be able to compete with other lightweight materials over and over again new steel grades are developed. Interesting steel grades, which are especially suitable for the lightweight construction in the automotive industry, are the multi-phase steels. Multi-phase steels reach already yield strengths over 1000 MPa. This is a challenge for the production engineering. Drawing, forming and cutting tools must be stiff and hard and/or coated, lubricants have to decrease friction to avoid damages induced by the high surface pressures. The designers have to consider the small forming capability by large radii or reduced drawing depths. To overcome these disadvantages new, innovative forming processes, e.g. laser assisted bending or roll forming, have to be developed. In the forming technique it is known that the forming limits can be increased by warm forming. But the conventional heating systems may cause unwanted changes of the material regarding to the structure and the mechanical properties. In the case of multi-phase steels e.g. the hard phases martensite and bainit can be transformed into ferrite and therefore the yield stresses can be changed clearly. In contrast to this laser assisted bending minimizes structural changes due to the local heating of the forming area. Beside the advantage, that only a small area of the bending part is exposed with a thermal load, the heating up with the laser permits high heating rates and also a controlling of the heating and cooling rates, so that the heating and cooling can be adapted to the material and its properties. In the context of this paper parameter studies with FE simulations of the laser assisted bending process are presented.

Thermal Management in Laser Assisted Machining: A Preliminary Study

2003 ◽  
Author(s):  
Tien-Chien Jen ◽  
Rajendra Jadhav ◽  
Yau-Min Chen ◽  
Samih Omari
Keyword(s):  
Structural Changes ◽  
Local Heating ◽  
Preliminary Investigation ◽  
Cutting Tools ◽  
Target Material ◽  
Material Structure ◽  
High Temperature Strength ◽  
Drilling Process ◽  
Mechanical And Thermal Properties ◽  
Surface Microstructures

The use of laser in manufacturing has gained considerable attention recently. In non-reactive processes, the laser beam is used either to machine, to weld, or to modify the target material structure by local heating. In addition to elevating the surface temperature of the target, this local heating may significantly alter the material crystalline structure; change its phase, and thus the electrical, mechanical and thermal properties. For reliability and consistency, it is necessary to control effectively the laser-based manufacturing processes. Specifically, the induced micro-structural changes due to the heat transfer mechanisms have to be analyzed. Most importantly, the thermal effect on the sub-surface microstructures and the generated thermal stress distribution need to be well quantified. The application of lasers in manufacturing has distinctive advange when dealing with ceramic material. The use of advanced ceramics has doubled in the past ten years, and is expected to grow at an even faster pace in the new millennium. The superior properties, such as low weight, high temperature strength and wear/corrosion resistance, of these structural ceramics make them the preferred materials in various applications including bearings, rollers/followers, valves, engines, cutting tools and even artificial joints in the human body. The major goal of this study is to develop an innovative laser-assisted drilling process through innovative tool design and cooling method. A preliminary investigation of the effect of donut-shaped laser heat input on the temperature distribution in the workpiece is studied numerically and experimentally.

Changes of Selected Structural and Mechanical Properties of the Strzelin Granites As Induced By Thermal Loads / Wpływ Obciążeń Termicznych Na Zmiany Niektórych Strukturalnych I Mechanicznych Właściwości Granitów Strzelińskich

2012 ◽  
Vol 57 (4) ◽  
pp. 951-974 ◽  
Author(s):  
Andrzej Nowakowski ◽  
Mariusz Młynarczuk
Keyword(s):  
Mechanical Properties ◽  
Nuclear Waste ◽  
Structural Changes ◽  
Structural Parameters ◽  
Total Porosity ◽  
Fracture Network ◽  
Qualitative Description ◽  
Temperature Changes ◽  
Heating And Cooling ◽  
Waste Repositories

Abstract Temperature is one of the basic factors influencing physical and structural properties of rocks. A quantitative and qualitative description of this influence becomes essential in underground construction and, in particular, in the construction of various underground storage facilities, including nuclear waste repositories. The present paper discusses the effects of temperature changes on selected mechanical and structural parameters of the Strzelin granites. Its authors focused on analyzing the changes of granite properties that accompany rapid temperature changes, for temperatures lower than 573ºC, which is the value at which the β - α phase transition in quartz occurs. Some of the criteria for selecting the temperature range were the results of measurements carried out at nuclear waste repositories. It was demonstrated that, as a result of the adopted procedure of heating and cooling of samples, the examined rock starts to reveal measurable structural changes, which, in turn, induces vital changes of its selected mechanical properties. In particular, it was shown that one of the quantities describing the structure of the rock - namely, the fracture network - grew significantly. As a consequence, vital changes could be observed in the following physical quantities characterizing the rock: primary wave velocity (vp), permeability coefficient (k), total porosity (n) and fracture porosity (η), limit of compressive strength (Rσ1) and the accompanying deformation (Rε1), Young’s modulus (E), and Poisson’s ratio (ν).

scholarly journals Dynamic Single-Fiber Pull-Out of Polypropylene Fibers Produced with Different Mechanical and Surface Properties for Concrete Reinforcement

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 722
Author(s):  
Enrico Wölfel ◽  
Harald Brünig ◽  
Iurie Curosu ◽  
Viktor Mechtcherine ◽  
Christina Scheffler
Keyword(s):  
Tensile Strength ◽  
Dynamic Loading ◽  
Melt Spinning ◽  
Structural Changes ◽  
High Surface ◽  
Single Fiber ◽  
Scanning Calorimetry ◽  
Matrix Interaction ◽  
Pull Out ◽  
Fiber Matrix

In strain-hardening cement-based composites (SHCC), polypropylene (PP) fibers are often used to provide ductility through micro crack-bridging, in particular when subjected to high loading rates. For the purposeful material design of SHCC, fundamental research is required to understand the failure mechanisms depending on the mechanical properties of the fibers and the fiber–matrix interaction. Hence, PP fibers with diameters between 10 and 30 µm, differing tensile strength levels and Young’s moduli, but also circular and trilobal cross-sections were produced using melt-spinning equipment. The structural changes induced by the drawing parameters during the spinning process and surface modification by sizing were assessed in single-fiber tensile experiments and differential scanning calorimetry (DSC) of the fiber material. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle measurements were applied to determine the topographical and wetting properties of the fiber surface. The fiber–matrix interaction under quasi-static and dynamic loading was studied in single-fiber pull-out experiments (SFPO). The main findings of microscale characterization showed that increased fiber tensile strength in combination with enhanced mechanical interlocking caused by high surface roughness led to improved energy absorption under dynamic loading. Further enhancement could be observed in the change from a circular to a trilobal fiber cross-section.

scholarly journals Investigation on the Surface Quality Obtained during Trochoidal Milling of 6082 Aluminum Alloy

Machines ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 75
Author(s):  
Nikolaos E. Karkalos ◽  
Panagiotis Karmiris-Obratański ◽  
Szymon Kurpiel ◽  
Krzysztof Zagórski ◽  
Angelos P. Markopoulos
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Process Parameters ◽  
Manufacturing Industry ◽  
High Surface ◽  
Cutting Tools ◽  
Cutting Speed ◽  
Depth Of Cut ◽  
High Surface Quality ◽  
Trochoidal Milling

Surface quality has always been an important goal in the manufacturing industry, as it is not only related to the achievement of appropriate geometrical tolerances but also plays an important role in the tribological behavior of the surface as well as its resistance to fatigue and corrosion. Usually, in order to achieve sufficiently high surface quality, process parameters, such as cutting speed and feed, are regulated or special types of cutting tools are used. In the present work, an alternative strategy for slot milling is adopted, namely, trochoidal milling, which employs a more complex trajectory for the cutting tool. Two series of experiments were initially conducted with traditional and trochoidal milling under various feed and cutting speed values in order to evaluate the capabilities of trochoidal milling. The findings showed a clear difference between the two milling strategies, and it was shown that the trochoidal milling strategy is able to provide superior surface quality when the appropriate process parameters are also chosen. Finally, the effect of the depth of cut, coolant and trochoidal stepover on surface roughness during trochoidal milling was also investigated, and it was found that lower depths of cut, the use of coolant and low values of trochoidal stepover can lead to a considerable decrease in surface roughness.

Metastability in Monolayer Films Transferred onto Solid Substrates by the Langmuir-Blodgett Method: IR Evidence for Transfer-Induced Phase Transitions

1994 ◽  
Vol 48 (10) ◽  
pp. 1196-1203 ◽  
Author(s):  
Fazale R. Rana ◽  
Suci Widayati ◽  
Brian W. Gregory ◽  
Richard A. Dluhy
Keyword(s):  
Fatty Acid ◽  
Conformational Changes ◽  
Structural Changes ◽  
High Surface ◽  
Solid Substrate ◽  
Water Interface ◽  
Monolayer Films ◽  
Langmuir Blodgett ◽  
Monomolecular Film ◽  
Air Water Interface

The rate at which a monomolecular film is deposited onto a solid substrate in the Langmuir-Blodgett process of preparing supported monolayer films influences the final structure of the transferred film. Attenuated total reflectance infrared spectroscopic studies of monolayers transferred to germanium substrates show that the speed at which the substrate is drawn through the air/water interface influences the final conformation in the hydrocarbon chains of amphiphilic film molecules. This transfer-induced effect is especially evident when the monolayer is transferred from the expanded region of surface-pressure-molecular-area isotherms at low surface pressures; the effect is minimized when the film molecules are transferred from condensed phases at high surface pressures. This phenomenon has been observed for both a fatty acid and a phospholipid, which suggests that these conformational changes may occur in a variety of hydrocarbon amphiphiles transferred from the air/water interface. This conformational ordering may be due to a kinetically limited phase transition taking place in the meniscus formed between the solid substrate and aqueous subphase. In addition, the results obtained for both the phospholipid and fatty acid suggest that the structure of the amphiphile may help determine the extent and nature of the transfer-speed-induced structural changes taking place in the monomolecular film.

Modeling and Design of Building-Integrated Thermoelectrics

2011 ◽  
Author(s):  
Leon M. Headings ◽  
Gregory N. Washington
Keyword(s):  
Thermal Response ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Conventional Heating ◽  
Net Energy ◽  
Arbitrary Boundary ◽  
Heating And Cooling ◽  
Temperature Oscillations ◽  
Wall Structures ◽  
And Control

The goal of this research is to develop a framework for replacing conventional heating and cooling systems with distributed, continuously and electrically controlled, building-integrated thermoelectric (BITE) heat pumps. The coefficient of performance of thermoelectric heat pumps increases as the temperature difference across them decreases and as the amplitude of temperature oscillations decreases. As a result, this research examines how thermal insulation and mass elements can be integrated with thermoelectrics as part of active multi-layer structures in order to minimize net energy consumption. In order to develop BITE systems, an explicit finite volume model was developed to model the dynamic thermal response of active multi-layer wall structures subjected to arbitrary boundary conditions (interior and exterior temperatures and interior heat loads) and control algorithms. Using this numerical model, the effects of wall construction on net system performance were examined. These simulation results provide direction for the ongoing development of BITE systems.

Vitamin B1 and B6 Retention in Milk after Continuous-Flow Microwave and Conventional Heating at High Temperatures

2001 ◽  
Vol 64 (6) ◽  
pp. 890-894 ◽  
Author(s):  
ISABEL SIERRA ◽  
CONCEPCIÓN VIDAL-VALVERDE
Keyword(s):  
High Temperatures ◽  
Continuous Flow ◽  
Vitamin B6 ◽  
Vitamin B1 ◽  
Raw Milk ◽  
Microwave Treatment ◽  
Conventional Heating ◽  
Conventional System ◽  
Tubular Heat Exchanger ◽  
Heating And Cooling

The effect of continuous-flow microwave treatment at high temperatures on the retention of vitamins B1 and B6 in raw milk with different fat content was evaluated. Results were compared with those obtained using a conventional system (tubular heat exchanger) with the same heating and cooling phases. Heat treatment of whole (3.4% fat) and skim (0.5% fat) milk at 90°C produced no losses of vitamin B1 or vitamin B6 (pyridoxamine and pyridoxal). However, at 110 and 120°C, while vitamin B1 content of milk remained constant, pyridoxamine increased (4 to 5% and 9 to 11%, respectively) and pyridoxal decreased (5 to 6% and 9 to 12%, respectively). Under the assayed conditions, no differences were observed between the content of these vitamins in conventionally and continuous-flow microwave-treated milk.

High surface area titanium phosphonate materials with hierarchical porosity for multi-phase adsorption

2010 ◽  
Vol 34 (6) ◽  
pp. 1209 ◽  
Author(s):  
Tian-Yi Ma ◽  
Xiu-Zhen Lin ◽  
Xue-Jun Zhang ◽  
Zhong-Yong Yuan
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Hierarchical Porosity ◽  
Multi Phase

Direct observation of three-dimensional transient temperature distribution in SiC Schottky barrier diode under operation by optical-interference contactless thermometry (OICT) imaging

2022 ◽  
Author(s):  
Keiya Fujimoto ◽  
Hiroaki Hanafusa ◽  
Takuma Sato ◽  
Seiichiro HIGASHI
Keyword(s):  
Temperature Distribution ◽  
Schottky Barrier ◽  
Hot Spot ◽  
Local Heating ◽  
Three Dimensional ◽  
Schottky Barrier Diode ◽  
Transient Temperature ◽  
Optical Interference ◽  
Transient Temperature Distribution ◽  
Heating And Cooling

Abstract We have developed optical-interference contactless thermometry (OICT) imaging technique to visualize three-dimensional transient temperature distribution in 4H-SiC Schottky barrier diode (SBD) under operation. When a 1 ms forward pulse bias was applied, clear variation of optical interference fringes induced by self-heating and cooling were observed. Thermal diffusion and optical analysis revealed three-dimensional temperature distribution with high spatial (≤ 10 μm) and temporal (≤ 100 μs) resolutions. A hot spot that signals breakdown of the SBD was successfully captured as an anormal interference, which indicated a local heating to a temperature as high as 805 K at the time of failure.

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