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Dual phase steels are being extensively considered as a structural material for automobiles because of the favourable combination of strength and formability. Crashworthiness of these new steels is an area of great importance. High strain rate testing is one approach to measure the ability of materials to absorb energy in a crash situation. The objective of this paper is to examine the effect of the deformation rate on the mechanical properties of dual-phase and multi-phase steels. Shear-punch experiments are conducted both at quasi-static and dynamic rates for this purpose. The ease of preparation of shear punch specimens compared to the tension specimen makes this approach attractive in evaluating key mechanical properties, such as ultimate tensile strength (UTS) and ductility limits, of automotive materials mostly in sheet forms.

The high strain rate deformation behavior of commercially available dual phase steel was studied by means of split Hopkinson bar apparatus in shear punch mode with an emphasis on the influence of microstructure. The cold rolled sheet material was subjected to a variety of heat treatment conditions to produce several different microstructures. Dual phase microstructures with different fractions of martensite were obtained by changing intercritical annealing temperature and time. Various microstructures of ferrite plus pearlite, or acicular ferrite/bainite, or bainite and martensite/carbide were obtained by changing the cooling rate after annealing. The effects of low temperature tempering and bake hardening treatment were also investigated for some selected specimens.

With the aim of producing innovative clutch actuation mechanisms for automotive transmissions, we are investigating a design based on power screws. The design strives to improve clutch actuation technology and minimize energy consumption by maintaining clutch lock-up independent of an external energy source. The system consists of a lead screw shaft-and-nut assembly, a clutch apply-plate, a set of wet clutch disks and a brushless DC motor. The clutch actuation assembly is separated from the clutch-pack via thrust bearings, which allows the use of a motor, while reducing the inertial load imposed by the conventional clutch-pack. A prototype of the design was fabricated and installed on a testbed, to mimic the installation of the actuator to replace the hydraulic components. A standard 12-disk clutch-pack of an automatic transmission was used within the apparatus. The formulation of the mathematical model of the entire testbed is described in this paper.

Tempered martensite assisted steels are of recent research interest for good strength and ductility combination. This paper discusses the effect of tempered martensite volume fraction on the final properties of cold rolled and subcritically annealed Al containing TRIP steel. The samples were TRIP annealed and the retained austenite volume fraction was measured using X-ray diffraction technique. The steel samples were subsequently cold rolled to obtain strain induced martensite, deformed ferrite and bainite in the microstructure. The final tempered martensite volume fraction corresponds to the initial retained austenite volume fraction of the steel. The cold rolled TRIP steel samples were subsequently subcritically annealed at 500°C for 1 hour to obtain tempered martensite, fine ferrite and bainite. Shear Punch testing was used to evaluate the mechanical properties. The properties are analyzed and the results are discussed.

This paper presents a control system for the thermoforming of large sheets. The system has three main purposes: Its primary purpose is for cycle-to-cycle control of the sheet temperature map as predicted by the thermoforming simulation. Its secondary purpose is to tune the simulation to the actual process through on-line characterization of some of the material and machine characteristics so that the simulation's predictions are reconciled with the machine sensors outputs. Lastly it can characterize on-line a number of independent and fast acting sub-models that allow for in-cycle control of some process parameters.