R=0.7 R=0.5 R=0.1

The goal of the project is to build and integrate fundamental and applied knowledge of materials science and fracture mechanics for design, life predictions, and development and optimization of light metal alloys for fatigue and fatigue crack growth (FCG) performance in structural applications.

During the 2nd year, major steps were further taken towards achieving these goals and disseminating the knowledge through publications and to industry. Highlights of the accomplishments include:• Establishing a library of reliable FCG data and mechanisms at

the micro-/nano-structural scale of various cast and wrought Al alloys at all growth stages;

• Building two-parameter design maps correlating loading conditions (ΔK, Kmax, R), crack propagation modes, and materials’ microstructures to be used in component design, performance evaluation, and material/process optimization;

• Formulating an original model incorporating the effects of crack size and material’s microstructure on the FCG response and a unified method predicting FCG data/behavior (without testing);

• Developing numerical tools with microstructural dependency as a basis for (i) simulating and predicting FCG at all stages and crack-phase interactions & (ii) accurately evaluating lifetimes.

These developments will facilitate the design of higher-performance, safer, and more reliable vehicles; enable weight reduction; and contribute to reductions in fuel consumption and CO2 emissions.

CAREER: On the Engineering of Light Metals for Enhanced Dynamic Properties and Fatigue Performance

Diana A. Lados, Worcester Polytechnic Institute, DMR 1151588

Numerical modeling techniques and results: extended finite element displacement approximation (below, left) and FCG simulations comparing stress contours in two Al cast alloys (below, right).

Changes in FCG mechanisms at the microstructural scale of an Al-7%Si-0.35%Mg cast alloy; optical side views (above), two-parameter design map (below, left), and the novel “small crack growth model” (below, right).

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Lower Region II Upper Region II Region III

Educational outreach programs have been designed and implemented to develop appreciation and interest in science, engineering, and materials science. These programs engage high school students and girls ages 9-13 to positively affect their understanding of our field and career choices, and they include:• A learning module on “Fatigue and Fracture of Metallic

Materials” for the ASM New England Materials Experience/Camp (offered for the first time in May 2013 and again in May 2014 to 70-80 high school students and teachers);

• A summer program, “Young Women in Science”, for girls grades 5-7 to introduce them to materials science and engineering at early stages (offered for the first time in July 2013 and again in July 2014 to 30-40 young girls).

Other avenues for disseminating the knowledge developed in this research include new symposia; the Integrative Materials Design Center (iMdc) at WPI, an industry-government-university consortium, founded and led by the PI, with members from all transportation sectors, national labs, and government; and a senior Aerospace Materials course developed and taught by the PI.Photos: ASM Materials Camp students participate in the “Fatigue and

Fracture” module (top and center left) and “Young Women in Science” Program students spend a day learning about materials and taking part in hands-on activities (center right and bottom)

CAREER: On the Engineering of Light Metals for Enhanced Dynamic Properties and Fatigue Performance

Diana A. Lados, Worcester Polytechnic Institute, DMR 1151588