Integrated Computational Materials Engineering: Modeling and Simulation Applied to Metals Processing: Materials and Manufacturing Process Modeling and Simulation
Sponsored by: MS&T Organization
Program Organizers: David Furrer, Pratt & Whitney
Wednesday 2:00 PM
October 19, 2011
Room: C213
Location: Greater Columbus Convention Center
Session Chair: Pamela Kobryn, AFRL
2:00 PM
Powder Metallurgy Simulations: Press-Sinter, Injection Molding: Randall German1; Seokyoung Ahn2; Suk Hwan Chung3; Seong Taek Chung4; Seong Jin Park5; Young Sam Kwon4; 1San Diego State University; 2University of Texas Pan American; 3Hyundai Steel Company; 4CetaTech, Inc.; 5Pohang University of Science and Technology
Computer simulation of powder metallurgy activities are quite advanced, including simulations of die compaction and injection molding, and other options. Although there is much advantage from such efforts, there are problems. The desire is to enable set-up of the operation, but the industrial processes are loosely controlled. As such, the powder metallurgy simulations focus on the use of minimal input data to help with process set-up, but are not targeted at accurate prediction of size, shape, microstructure, or properties. Within this limitation, the simulations are accurate, but not able to deliver process specifications for tolerance demands of 0.01 mm. To achieve this level of accuracy requires model future upgrades, such as inclusion of frictional tool heating. Unfortunately, industrial operations are not precisely specified, a factor limiting the simulations where nominal characteristics are assumed.
2:20 PM
Integrated Computational Modeling of Welding – Development to Deployment: Sudarsanam Babu1; 1Ohio State University
Welding is a critical process for manufacturing of small and large components. Even with extensive use, optimization of welding processes involves trial and error experimentation. Integrated computational modeling is considered as a viable pathway to address this challenge. The presentation will discuss methodologies based on fundamental understanding of underlying physics, as well as, progress made due to high performance computing infrastructure with examples. The examples will range from predictions of heat- and mass-transfer, residual stress, distortion, microstructure and mechanical properties. However, the adoption of integrated modeling by industry has been slow. The first reason is related skepticism in terms of reducing costs and delivery times and improving quality for welded construction through modeling. The second reason is due to lack of a standard verification and validation (V&V) documents to build a technical case. Technological and standardization pathways to close the above gap are being pursed by international organizations.
2:40 PM
Numerical Analysis of Welding Induced Residual Stresses Regarding Dependency of Martensite Start Temperature on Austenite Grain Size: Christoph Heinze1; Christopher Schwenk1; Michael Rethmeier1; Sudarsanam Babu2; 1BAM Federal Institute for Materials Research and Testing; 2The Ohio State University
Austenite grain growth during welding is a critical factor for controlling weld microstructure in addition to nominal composition and thermal cycles. Recently, experimental data suggesting a decrease in martensite start temperature (Ms) with a decrease in austenite grain size (AGS) has been published. However, the actual sensitivity of this phenomenon on residual stresses evolution in the heat affected zone (HAZ) has not been investigated, yet. Therefore, the present investigations include an enhanced numerical model with austenite grain growth and relating the same to Ms-temperatures. Subsequently, initial residual stress calculations are compared with calculations considering the AGS dependency. This comparison is performed for common low alloy steel with minimum yield strength of 355 MPa (S355J2+N). The results clarify the influence of austenite grain size on the residual stress development. Finally, no significant influence of Ms-temperature variations due to AGS changes on welding-induced residual stress was found.
3:00 PM
Predicting Residual Stress and Dimensional Change Due to Heat Treatment of Steel Parts: Blake Ferguson1; Zhichao Li1; Andrew Freborg1; 1Deformation Control Technology, Inc.
Distortion of steel parts during heat treatment is a major problem for manufacturers and requires much time and effort to correct. A volumetric expansion occurs as austenite transforms to martensite, bainite, or ferrite/pearlite during quenching. Internal stresses due to thermal gradients and non-uniform phase transformation are the main causes of distortion. The quenching process imparts residual stress, which affects part performance. Residual surface compression enhances fatigue life, while residual surface tension degrades fatigue life. A combined carburization and quenching process is used to increase surface strength and impart compressive residual surface stress. Prediction of residual stress and distortion must include prediction of metallurgical phase transformations that occur during heat treatment. Heat treatment modeling software, DANTE, will be used to demonstrate to understand the part response to quenching. With knowledge of the distortion and residual stress, the process can be modified to improve performance and manufacturing economics of steel parts.
3:20 PM Break
4:00 PM
Simulation of Rotational Welding Operations: Michael Preuss1; Philip Withers1; 1University of Manchester
The principle of rubbing two objects together thereby causing frictional heating is one dating back many centuries. It now forms the basis of many mature, as well as novel, friction joining, surfacing, and processing techniques. When joining objects by friction, the work-pieces are rubbed together under high pressure to generate the required frictional energy and the parts form a solid state joint without melting. The talk will give a brief historical overview of the process, describe its impact on microstructure variations and residual stresses generation in the weld region before giving an overview of the modelling tools that have been developed for rotational friction welding to date. Challenges related to obtaining the effective ‘friction’ response of the materials will be discussed as well as the development of the thermal and mechanical aspect of the models. Examples will be given where residual stress and microstructural models were developed and validated.
4:20 PM
Computer Modeling of Induction Heat Treating: Things to be Aware Of, Things to Avoid: Valery Rudnev1; 1Inductoheat Inc.
Great majority of commercial codes used for computer simulation of induction thermal processes are all-purpose programs. Regardless of well-recognized capabilities of that software, some of generalized programs experience difficulties in properly modeling certain features of induction heat treating. This includes but not limited to the presence of thermal refractory, heated workpiece can simultaneously move, rotate or oscillate in respect to induction coil, presence of non-uniform initial temperature distribution, comet-tail effect, pre- and post-heating effects in modeling induction scan hardening. Presentation discusses novel subject-oriented computer simulation software developed for needs of induction heat treating. Case studies of computer simulation of induction surface and through hardening, tempering, stress relieving, annealing, shrink fitting, brazing and other applications will be discussed here as well.
4:40 PM
Modeling and Simulation of Machining: Christian Fischer1; 1Scientific Forming Technologies Corporation
Whether it is used as a product finishing process, or only for making tools for a forged, cast, stamped, or molded part, machining impacts a very wide range of manufacturing processes. The economics of machining are governed largely by the cost of owning and maintaining equipment and by labor costs. Reducing the production cost per part frequently means minimizing the time that part is being processed on a machine while still maintaining acceptable part quality. As with any process, computer modeling of machining processes offers the opportunity to reduce or eliminate the cost associated with physical prototype tests, and give a better understanding of phenomena not easily studied in experiments. This presentation will examine the technology behind metal cutting simulation, review the data requirements and testing methods, and highlight some industrial and emerging applications.
5:00 PM
Stress-Relief Simulation: Dennis Buchanan1; 1UDRI
Bulk residual stresses from material manufacture and machining as well as surface treatment residual stresses from shot peening exist in most engineered components and structures. These bulk and surface residual stresses continually evolve with thermal and mechanical loading history starting from the manufacturing stage and throughout the service life of the component. Understanding the mechanisms and models behind stress relaxation (relief) is critical to engineering improvements in manufacture, machining, and design of components. Parametric simulations with stress relief models can be used to optimize processes that minimize residual stresses in manufacture and maximum design life. This presentation compares stress relief simulation models with approximate solutions and simple constitutive models to advanced numerical solutions with temperature and history dependent constitutive material models. Experience has shown that any stress relief simulation should start with a simple approximate solution and progress to a more advanced solution with rigorous scrutiny of the simulation results.