Session 18: Materials Processing

Chairs:

Márcio Ziviani
Departamento de Engenharia Mecânica UFMG

Comissão Organizadora e Editorial do ENCIT 2000
Departamento de Endgenharia Mecânica Universidade Federal do Rio Grande do Sul






s18p01

SOME CAUSES OF DIFFERENCES BETWEEN ANALYTICAL RESULTS AND TEMPERATURE MEASUREMENTS IN WELD HAZ

Luciano Amaury dos Santos - [email protected]
Antônio Fábio Carvalho da Silva - [email protected]
Carlos Enrique Niño - [email protected]
Augusto José de Almeida Buschinelli - [email protected]
Departamento de Engenharia Mecânica, UFSC
CEP 88040-900, Florianópolis, SC, Brasil

Abstract.  In this paper are discussed some causes of the differences observed between temperature measurements, taken through thermocouples inserted in the weld heat affected zone (HAZ), and analytical results.  In this discussion (partially based in numerical solutions) some effects disregarded in the analytical solution are considered: that of the latent heat of fusion and that of the temperature dependence of the thermal conductivity (the effect of the stirring present inside the weld pool can be approximately taken in account by the use of an artificially augmented conductivity value for the molten material).  All these effect seem to be important in experiments like those considered in the present work, but not at the point of making the analytical solution (and its comparison with the measurements) uninteresting.  Special attention is given to welding with thermal pulsing.

Keywords: Welding, Heat conduction, Temperature measurement
 
 



s18p04

NEW BOUNDS FOR THERMAL CONDUCTIVITY OF RECYCLED POLYMERIC MATRIX COMPOSITES

Antonio F. _ Avila { [email protected]
Universidade Federal de Minas Gerais, Composites Laboratory
Department of Mechanical Engineering, 31270{901 Belo Horizonte, Brazil

Polymeric matrix composites (PMC) are used in engineering applications as they present low density and high strength. However, they are not used in large{scale
applications due to their high cost. The large variety of thermoplastic matrices allow us to experiment di_erent types of resin combinations creating the so{called melt-blended matrices. In this model, a binary combination of thermoplastics is used to form a fully recycled melt-blended matrix. The HDPE/PET matrix is assumed to be composed by PET spheroidal inclusions diluted in a HDPE substrate, and the resulting matrix is used to form a unidirectional laminated polymeric matrix composite. Due to chemical reac- tions involved during the matrices combination process and between the resulting matrix and the E-glass _bers, the weak interface _ber/matrix condition must be considered. To model the thermal-elastic behavior of HDPE/PET-E glass _ber composites a double step homogenization procedure is proposed. The concentric spheres model is applied to obtain the melt-blended matrix e_ective properties, and to describe the overall composite behav- ior the composite assemblage model under weak interface condition is considered. The new expression proposed for the e_ective transverse thermal conductivity is based on the analogy between shear loading and conductivity. The numerical simulations are compared against analytical models, Hashin and Rosen, and the representative volume element approach with good agreement.

Keywords:Bound for Thermal Conductivity, Laminated Polymeric Matrix Composites, Recycled composites
 
 



s18p08

TEXTURE AND PROPERTIES OF WARM ROLLED INTERSTICIAL FREE STEELS

José R. G. Matheus - [email protected]
Andréa Machado Lopes -  [email protected]
Hani Hussein ALY El-Sharawy - [email protected]
Carlos Sérgio da Costa Viana - [email protected]
Instituto Militar de Engenharia, Department of Mechanical and Materials Engineering
Praça General Tibúrcio 80, Praia Vermelha, CEP: 22290-270 - Rio de Janeiro, RJ, Brazil

The Interstitial Free ( I. F. ) steels are novel materials of Ultra High Drawability used extensively in modern car industry, especially for the fabrication of car bodies of intricate and modern design. The exceptional formability is attributed to the specific chemical composition of very low carbon ( ~ 0.003-0.006 % ), titanium microadditions ( ~ 0.06-0.09 % ), and to the development of desired crystallographic texture during the steel thermomechanical processing. Stable carbides are formed in the austenite range, rendering the steel matrix almost carbon free, which allows high  thickness reductions in the ferrite range. An I. F. steel was rolled at 600oC and 400oC under 60 % reductions, and cooled in air. At these temperatures, recrystallization is inhibited and the texture developed during rolling may be analyzed at room temperature. Texture was determined from Electron Back Scattering Diffraction (EBSP) using Orientation Imaging Microscopy (OIM). The Crystal Orientation Distribution Functions (CODF) correspond to the average texture across the sample thickness, and along the rolling direction. The results were compared with the CODF for samples rolled at room temperature. Independent of the rolling temperature, sample annealing returns similar texture components. These results encourage the development of continuous IF steels rolling schedules spanning down to lower temperatures

Keywords: Interstitial Free Steel, Warm Rolling, Crystallographic Texture, Sheet Drawability