Materials Joining Engineering Projects

In addition to their capstone senior design and other class projects, LeTourneau MJE students have a unique opportunity to conduct materials joining research and development at the undergraduate level, most of which is sponsored by the same companies that hire our graduates.  The critical thinking, problem-solving and project management skills that are developed in the applied research environment, as well as the self-direction, inquisitiveness and creativity that it fosters, make our graduates especially attractive in the career marketplace.  Below are a few examples.

Weldability of High-Performance Steels

This project led by Professor Yoni Adonyi and sponsored by the American Iron and Steel Institute (AISI) was aimed at developing welding and preheating guidelines for newly developed high-performance steels (HPS) for America’s bridges.  Participants in the project included the US Navy, major steel producers, and welding consumable manufacturers such as Lincoln Electric, Hobart/ITW and ESAB.
New plate steels having 70 and 100 ksi yield strengths, good toughness and weathering (corrosion resistance) characteristics needed optimum welding consumables and preheat data to achieve property matching and avoid hydrogen-induced cracking.
Hundreds of small-scale weldability tests called Gapped Bead-on-Plate (G-BOP) were performed using several different consumables and diffusible hydrogen levels.  Welding processes used were Shielded Metal Arc (SMAW) Submerged Arc (SAW), Gas Metal Arc (GMAW) and Flux Cored Arc (FCAW) Welding.  More than 25 students were involved in experiment design, analysis and reporting.
Variability in testing and validity of preheat predictions was extensively studied using finite element (FE) analysis and robotic welding was used to reduced variability in testing.  Subprojects included waveform and droplet transfer mode analysis, bead geometry and cooling rate effects, specimen preparation using abrasive waterjet cutting.
Results were made available on the AISI website under HPS Manufacturing Guidelines and several papers and technical presentations were made.

Adhesive Bonding Research

This project led by Professor Bill Schroeder (retired) was sponsored by the Texas Higher Education Coordinating Board and involved almost twenty students from 2000 to 2002.
Lucent Technologies needed to replace welding of power module cabinets with a more economical joining process, also capable of withstanding seismic loading.  Adhesive Bonding was chosen as an alternative to Gas Metal Arc Welding (GMAW), and all of the corner joints had to be redesigned using finite element (FE) analysis to accommodate industrial adhesives supplied by 3-M and other major suppliers.
The actual shear strength of various epoxies and acrylics was measured as a function of surface preparation type, joint gap size, curing temperature, etc.  Several hundred such combinations were tested and their properties optimized.
It was found that major economic benefits could also be reaped by choosing the strongest adhesive that cured at the same temperature (200°C) as the paint, enabling the cabinet to be assembled, painted and cured in the same fixture.
Finally, seismic testing was performed at Southwest Research Institute, where the adhesively bonded cabinets clearly outperformed the welded ones under simulated earthquake events reaching Magnitude 9.0.
The resulting adhesive bonding design, manufacturing and testing guidelines were made available on a website and were published in two articles of The Fabricator.

High Temperature Properties of Welded Tubular Product

This project led by Professor Yoni Adonyi and sponsored by Lone Star Steel Company was aimed at understanding the fundamental metallurgical reactions leading to reduced toughness in Electric Resistance Welded (ERW) AISI 4130 steel pipe following hot reduction.
A rarely seen low-toughness microstructure called Widmanstätten Ferrite (WF) was observed under certain strain and temperature conditions.  Physical simulations were therefore conducted to isolate tensile and compressive strain effects from thermal effects on WF formation using the Gleeble 1500 thermomechanical simulator.
Five students worked on ‘translating’ stretch mill strain and temperature data to program the simulator, which could then reproducibly create the appropriate conditions in a controlled atmosphere.  Critical temperature, strain rate and cooling rate effects were identified using this approach.
The results were translated back into mill operating practices involving different pipe entry temperatures and final cooling rates, and the WF microstructure was successfully eliminated.
Result were published in the technical literature and two related talks were given at conferences.