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Fatigue

Iowa State University

Articles 1 - 4 of 4

Full-Text Articles in Engineering Science and Materials

Electrically Induced Strain And Polarization Fatigue In Lead-Free Ceramics, Daniel Sommer Jan 2017

Electrically Induced Strain And Polarization Fatigue In Lead-Free Ceramics, Daniel Sommer

Graduate Theses and Dissertations

Piezoelectric ceramics have traditionally been used in commercial applications such as actuators and sensors. By far the most popular piezoceramics currently in use are Pb(Zr,Ti)O3-based (PZT) ceramics. PZT ceramics are able to produce large strain and polarization with the application of an electric field, and this is due to the Morphotropic phase boundary (MPB). A MPB is associated with the boundary between tetragonal and rhombohedral perovskite phases. A disadvantage of PZT ceramics is that they contain ≥ 60 wt. % of lead. Since lead is toxic, this poses an environmental and health hazard because lead is released into the ...


Design And Development Of High-Performance Lead-Free Piezoelectric Ceramics, Xiaoming Liu Jan 2015

Design And Development Of High-Performance Lead-Free Piezoelectric Ceramics, Xiaoming Liu

Graduate Theses and Dissertations

Piezoelectric ceramics have been widely used in the commercial applications of actuators, sensors, etc. Nowadays, Pb(Zr,Ti)O3-based (PZT) ceramics, which contain ≥ 60 wt.% of lead, dominate the market due to their excellent electromechanical properties. The large electric field induced polarization and strain developed in PZT piezoceramics are intimately related to the morphotropic phase boundary (MPB). This has been attributed to the coexistence of tetragonal and rhombohedral perovskite phases. However, toxic lead severely threatens the environment and human health, as a significant amount of lead is released into the air during the fabrication and disposal. Thus, there is an ...


Effects Of Alloying Elements On The Microstructure And Fatigue Properties Of Cast Iron For Internal Combustion Engine Exhaust Manifolds, David Jon Eisenmann Jan 2015

Effects Of Alloying Elements On The Microstructure And Fatigue Properties Of Cast Iron For Internal Combustion Engine Exhaust Manifolds, David Jon Eisenmann

Graduate Theses and Dissertations

In the design of exhaust manifolds for internal combustion engines the materials used must exhibit resistance to corrosion at high temperatures while maintaining a stable microstructure. Cast iron has been used for manifolds for many years by auto manufacturers due to a combination of suitable mechanical properties, low cost, and ease of casting. Over time cast iron is susceptible to microstructural changes, corrosion, and oxidation which can result in failure due to fatigue. This thesis seeks to answer the question: “Can observed microstructural changes and measured high temperature fatigue life in cast iron alloys be used to develop a predictive ...


A Quantitatively Accurate Theory Of Stable Crack Growth In Single Phase Ductile Metal Alloys Under The Influence Of Cyclic Loading, Peter Huffman Jan 2014

A Quantitatively Accurate Theory Of Stable Crack Growth In Single Phase Ductile Metal Alloys Under The Influence Of Cyclic Loading, Peter Huffman

Graduate Theses and Dissertations

Although fatigue has been a well studied phenomenon over the past century and a half, there has yet to be found a quantitative link between fatigue crack growth rates and materials properties. This work serves to establish that link, in the case of well behaved, single phase, ductile metals. The primary mechanisms of fatigue crack growth are identified in general terms, followed by a description of the dependence of the stress intensity factor range on those mechanisms. A method is presented for calculating the crack growth rate for an ideal, linear elastic, non-brittle material, which is assumed to be similar ...