Research areas
Material Properties and Characterization
Prof. H.T. Kang, Prof. G.T. Kridli, Prof. P.K. Mallick
Prof. P. Mohanty, Prof. E.A. Orady, Prof. G. Reyes-Villanueva
Durability of aluminum tailor-welded blanks
This study is addressing the fatigue durability of tailor welded blanks (TWBs) made with different gage mismatch. The blanks are joined using friction stir welding. Test specimens, machined from different sections of rectangular pans made with TWBs, are subjected to stress-controlled fatigue tests. Weld orientation relative to the loading direction, specimen location along the welded seam and pre-straining are three of the parameters being examined for their effects on fatigue life. The results from this study will be useful in designing tailor-welded blanks in fatigue-critical components.
Fatigue of automotive thermoplastics
As the use of filled and unfilled thermoplastics in automotive applications increases, the need for determining the fatigue performance of these materials becomes critically important. This study is considering the effects of design and process parameters on the fatigue performance of talc-filled polypropylene and glass fiber reinforced polyamide-6. The ultimate objective of this study is to develop fatigue design guidelines for thermoplastics similar to those used for metals. A part of this project involves the development of generalized constitutive models for semi-crystalline polymers, such as polypropylenes and polyamides, which can be used in large deformation analysis of these materials using finite element method. A variety of test conditions are considered in this study, including creep, stress relaxation, loading-unloading and interrupted loading. The viscoplastic nature of these polymers is taken into account in developing the constitutive equations.
Self-piercing riveted and riv-bonded joints in aluminum alloys
This experimental study concentrates on the static and fatigue behavior of self-piercing riveted joints in Al 6111-T4 and Al 5754-0. For the 5754 alloy, riv-bonded joints containing both self-piercing rivets and adhesive are also considered. The objectives of this study are (1) to determine the effects of self-piercing riveting process variables on the fatigue characteristics of these joints, (2) to develop an understanding of the fatigue failure mechanisms and, (3) to explore methods of enhancing the fatigue life of these joints. Material properties local to the riveted joints are influenced by the riveting process and are found to be the principal controlling factor in the fatigue failure of these joints.
Processing and Characterization of the Mechanical Properties of Novel Lightweight Multifunctional Hybrid Structures.
The objectives of the research are to develop, to evaluate and to model the mechanical behavior of high performance-lightweight multifunctional hybrid structures attractive to the aerospace, marine and military industries. The hybrid systems will consist of skins based on a new composite based on the latest impact resistant synthetic fibers with a high performance epoxy matrix developed for aerospace and advanced applications and novel 3/2 fiber-metal laminates based on the aforementioned advanced composite and an aluminum alloy with high strength and ductility; the core will consist of an energy absorbing metallic foam. Initial attention will focus on optimizing and characterizing the level of adhesion between the skins and core materials. Once this has been achieved, the static mechanical properties and the low velocity impact response of the hybrid structures will be investigated and modeled.
Dynamic denting characteristics of sheet materials
The objective of this study is to determine the effects of cold-work, paint-baking temperature and alloy composition on both static and dynamic dent energies of aluminum sheets considered for automotive body applications. A drop-weight impact machine is used for creating dents under low to medium strain-rate dynamic conditions. Static denting is created at very low strain rates. Theoretical models for predicting denting behavior are also being developed.
Influence of microstructure on corrosion behavior of magnesium alloys
The objective of this project is to conduct a systematic investigation of corrosion characteristics of cast magnesium alloys, such as AZ91D and AM50, considered for engine applications. The study includes both corrosion tests and mirostructural examination. The corrosion environment includes both aqueous solution and engine coolant. The effect of microstructures produced by sand casting, die-casting and thixomolding on the corrosion behavior is the main focus of this study.
Joining
Prof. P.K. Mallick, Prof. H-T Kang
Self-piercing riveted and riv-bonded joints in aluminum alloys
This experimental study concentrates on the static and fatigue behavior of self-piercing riveted joints in Al 6111-T4 and Al 5754-0. For the 5754 alloy, riv-bonded joints containing both self-piercing rivets and adhesive are also considered. The objectives of this study are (1) to determine the effects of self-piercing riveting process variables on the fatigue characteristics of these joints, (2) to develop an understanding of the fatigue failure mechanisms and, (3) to explore methods of enhancing the fatigue life of these joints. Material properties local to the riveted joints are influenced by the riveting process and are found to be the principal controlling factor in the fatigue failure of these joints.
Joining Aluminum and Nylon sheet
A study is conducting to investigate a potential joining method to permanently join Aluminum with Nylon sheets. The tool used in this process is very similar to the friction stir spot welding tool. This joining method utilizes heat from friction between the tool shoulder and the Aluminum sheet to be joined with the Nylon sheet. Aluminum sheet metal is placed on top of the Nylon sheet and the rotating tool is plunged into the Aluminum sheet to form the joint created due to the melted surface of the Nylon sheet around the center of the weld nugget and the mechanical interlock due to the deformation of Aluminum into the Nylon sheet. Spot lap shear joint specimens were formed to investigate the effect of several parameters such as tool geometry, tool RPM, tool dwell time, tool plunge depth and tool feed rate. Tensile tests were conducted to evaluate the joint strength and micro-graphical observations were conducted to investigate the failure mechanisms of the joint. Furthermore, the effects of knurling and chemical treatment on the Aluminum surface to be contacted to Nylon are also studied in this research. The materials used in this study are Aluminum alloy 6111 and Nylon 6-8202.
Machining
Prof. C. Lee, Prof. P.K. Mallick, Prof. E.A. Orady
Dynamic Models and Estimation for Batch Grinding Operations
The batch grinding process is characterized by multiple data streams sampled at different frequencies. A new modeling and estimation strategy is proposed as a method of integrating the fast sampled sensor signals and the off-line measured part qualities for monitoring and control of the batch grinding operation. After a nonlinear state space model is derived from existing analytical models in literature, a multi-rate estimation scheme is developed for estimation of part qualities based on extended Kalman filters. It has been shown that utilizing the off-line measurement data along with the continuity of the continuous state variables provide significant benefits to estimation tasks.
Intelligent Modeling and Control of Hard Disk Manufacturing
An intelligent control scheme for disk grinding in the hard-disk-drive industry is developed. The objective is to achieve the required dimensional accuracy of ground parts based on process I/O relationships captured in a radial basis function network (RBFN) model. A novel autonomous training algorithm is developed and used for construction of RBFN models with minimal human assistance. The thickness control scheme proposed in this project is based on a nonlinear inverse model of the disk grinding process. In order to account for the process variations resulting from uncertainties and changes in operating conditions, the controller is supplemented with an on-line turning algorithm. The performance of the proposed control scheme is evaluated by extensive simulation studies with experimental data. A Windows-based software written in C++ language with convenient graphical user interface was developed for easier use and future expansion of the proposed modeling and control schemes.
Run-to-Run Optimization of the Batch Grinding Process
A new approach based on model-based optimization scheme is proposed in order to deal with a general class of grinding optimization problems. The process variation is compensated by updating the model at the end of each run based on post-process measurement of part qualities.
Plastics-and Composites-Processing
Prof. P.K. Mallick, Prof. G. Reyes-Villanueva
Development of aluminum-composite hybrid tubes for automotive space-frame structure
In this research, composite-metal hybrid tubes are being developed as the structural elements of a lightweight automotive space-frame. One major objective of this research is the development of manufacturing process for these tubes. Studies so far have shown that hybrid tubes have higher stiffness and better static crush resistance over either the metal or composite tubes. Joining of tubular elements to form the space-frame structure is also being studied.
Development of a new low-cost environmentally friendly lightweight thermoplastic- based composite/metal hybrid system.
The main objective of this research program is to develop a new environmentally friendly low-cost lightweight thermoplastic-based composite/metal hybrid system attractive to the automotive and aerospace industries. The hybrid systems will be based on polypropylene-based composites and automotive and aerospace grade aluminum alloys.
Development of thermoplastic matrix composite beams and tubes for structural automotive applications
The objectives of this research are as follows:
- establish design and processing data for several low-cost thermoplastic matrix composites,
- develop a high-speed press forming process (similar to stamping for steel) for making thermoplastic matrix beams and tubes and,
- develop cost-benefit-design-processing feasibility of using thermoplastic matrix matrix composites for automotive body, chassis and frame members.
This research is considering not only the press forming process development, but also vibration welding of thermoplastic matrix composites. This latter process will be used to join two half sections of thermoplastic matrix composite beams and tubes to make a complete section.
Investigation of slurry preforming process parameters for SRIM composite skid plate development
The slurry process produces near net-shape preforms at a relatively cost and is being considered for high volume production of automotive composite parts. The purpose of this study is to investigate the slurry process parameters that influence the quality of slurry preforms and the properties of SRIM composite skid plates made from these preforms. Some of the preform quality issues are fiber distribution, fiber orientation, permeability, etc. This investigation will help establish the processing window for producing preforms with consistent quality and better properties.
Formability of Thermoplastic Lightweight Fiber-Metal laminates
Major objectives of this investigation are to evaluate and to establish the formability limits and the forming procedures to shape a final hybrid part of thermoplastic-based FMLs for automotive applications. Additional goals include the characterization of the deformation mechanisms occurring during press forming operations.
Metal Forming
Prof. H-T Kang, Prof. G.T. Kridli, Prof. P.K. Mallick
Prof. E.A. Orady, Prof. G. Reyes-Villanueva
Springback characteristics of aluminum alloys
In this study, the springback characteristics of aluminum alloy AA 5754 under combined tension and bending loads are being examined. The objective of this study is to determine the effects of cold work, annealing, bend radius and clamping on the springback of this 5000-series alloy. Analytical models are being developed that can predict the springback in stretch-bending operation of sheet materials. Results from this study can be used to examine the possibility of reducing springback of this alloy and other sheet materials.
Effects of material and process variables on tube hydroforming: simulation and experiments
This study involves both simulation and experiments on hydroforming of straight as well as curved tubes. The objective of this study is to examine the effects of both material and process variables on the thickness variation, shape generation and process limits in tube hydroforming operations. The first part of the work considered straight tube hydroforming with both high pressure as well as sequential pressure application. The second part of the work will concentrate on hydroforming of curved tubes.
Development of Simulation Tools for Superplastic Forming of Aluminum Sheet
The objective of this project is to develop the numerical tools required to model the superplastic forming process of aluminum sheet. Additionally, simulation tools will be used to link finite element models to the material feasibility maps in order to estimate the post-formed properties of the formed panel.
Formability Analysis of Sandwich Panels
This study investigates numerically and experimentally the formability of two Fiber-Metal Laminate systems based on a thermoplastic self-reinforced polypropylene and a glass fiber polypropylene composite materials.
For more information, please contact:
Prof. P. K. Mallick,
Director of The Center for Lightweighting Automotive Materials and Processing
4901 Evergreen Road, Dearborn, MI 48128, USA
Phone: 313-593-5119
Fax: 313-593-5386
E-mail: pkm@umich.edu