Fatigue life prediction of critical metallic components based on strain energy density

The realistic loading condition in most of the mechanical applications is cyclic where fatigue failure is the most possible failure mode. Fatigue failure can occur under the stress levels well below the static strength of the material. Total fatigue toughness is a new energy-based approach for fatigue modeling that has shown promising correlation with fatigue life of engineering metals, shape memory alloys and polymeric materials. In total fatigue toughness method, fatigue damage parameter is defined as the sum of dissipated strain energy density (Wd), which is calculated as the area encompassed by the loading and unloading paths in a stress-strain graph, and tensile elastic strain energy density (W_e^+), which is defined as the maximum linear-elastic strain energy density that is stored in the material per each cycle. In this study, we have investigated applicability of the total fatigue toughness method on fatigue life prediction of popular engineering metals, i.e. steel, aluminum and titanium. To this end, strain-controlled fatigue tests with different strain ratios and maximum strains were conducted on specimens designed according to ASTM standards. For each of the experiments the total fatigue toughness damage parameter was calculated and the correlation with experimentally observed fatigue lives were evaluated. The results showed that the total fatigue toughness damage parameter can closely correlate the experimental fatigue data obtained for three types of materials under different mean strain conditions

Spanning Trees and Spanning Eulerian Subgraphs with Small Degrees. II

Let $G$ be a connected graph with $X\subseteq V(G)$ and with the spanning forest $F$. Let $\lambda\in [0,1]$ be a real number and let $\eta:X\rightarrow (\lambda,\infty)$ be a real function. In this paper, we show that if for all $S\subseteq X$, $\omega(G\setminus S)\le\sum_{v\in S}\big(\eta(v)-2\big)+2-\lambda(e_G(S)+1)$, then $G$ has a spanning tree $T$ containing $F$ such that for each vertex $v\in X$, $d_T(v)\le \lceil\eta(v)-\lambda\rceil+\max\{0,d_F(v)-1\}$, where $\omega(G\setminus S)$ denotes the number of components of $G\setminus S$ and $e_G(S)$ denotes the number of edges of $G$ with both ends in $S$. This is an improvement of several results and the condition is best possible. Next, we also investigate an extension for this result and deduce that every $k$-edge-connected graph $G$ has a spanning subgraph $H$ containing $m$ edge-disjoint spanning trees such that for each vertex $v$, $d_H(v)\le \big\lceil \frac{m}{k}(d_G(v)-2m)\big\rceil+2m$, where $k\ge 2m$; also if $G$ contains $k$ edge-disjoint spanning trees, then $H$ can be found such that for each vertex $v$, $d_H(v)\le \big\lceil \frac{m}{k}(d_G(v)-m)\big\rceil+m$, where $k\ge m$. Finally, we show that strongly $2$-tough graphs, including $(3+1/2)$-tough graphs of order at least three, have spanning Eulerian subgraphs whose degrees lie in the set $\{2,4\}$. In addition, we show that every $1$-tough graph has spanning closed walk meeting each vertex at most $2$ times and prove a long-standing conjecture due to Jackson and Wormald (1990).Comment: 46 pages, Keywords: Spanning tree; spanning Eulerian; spanning closed walk; connected factor; toughness; total exces

A Menu Of Minimum Wage Variables For Evaluating Wages and Employment Effects: Evidence From Brazil

The international literature on minimum wage greatly lacks empirical evidence from developing countries. Brazil’s minimum wage policy is a distinctive and central feature of the Brazilian economy. Not only are increases in the minimum wage large and frequent but also the minimum wage has been used as anti-inflation policy in addition to its social role. This paper estimates the effects of the minimum wage on both wages and employment using panel data techniques and monthly household data from 1982 to 2000 at individual and regional levels. A number of conceptual and identification questions is discussed, for example: (1) Various strategies on how to best measure the effect of a constant (national) minimum wage are summarized in a “menu” of minimum wage variables. (2) An employment decomposition that separately estimates the effect of the minimum wage on hours worked and on the number of jobs is used. (3) Robustness checks accounting for sorting into the informal and public sectors are performed. Robust results indicate that an increase in the minimum wage strongly compresses the wages distribution with moderately small adverse effects on employment.minimum wage, wage effect, employment effect, informal sector, Brazil

A Menu of Minimum Wage Variables for Evaluating Wages and Employment Effects: Evidence from Brazil

The international literature on minimum wage greatly lacks empirical evidence from developing countries. Brazil’s minimum wage policy is a distinctive and central feature of the Brazilian economy. Not only are increases in the minimum wage large and frequent but also the minimum wage has been used as an anti-inflation policy in addition to its social role. This study estimates the effects of the minimum wage on both wages and employment using panel data techniques and Brazilian monthly household data from 1982 to 2000 at individual and regional levels. A number of conceptual and identification questions is discussed, for example: (1) Various strategies on how to best measure the effect of a constant (national) minimum wage are summarized in a “menu” of minimum wage variables and used to estimate wage and employment effects. (2) An employment decomposition that separately estimates the effect of the minimum wage on hours worked and on the number of jobs is used. Robust results indicate that an increase in the minimum wage strongly compresses the wages distribution with moderately small adverse effects on employment.minimum wage; wage effect; employment effect; informal sector; public sector; Brazil

The effects of the minimum wage on wages and employment in Brazil: a menu of minimum wage variables

The international literature on minimum wage strongly lacks empirical evidence from developing countries. In Brazil, not only are increases in the minimum wage large and frequent - unlike the typically small increases focused upon in most of the existing literature - but also the minimum wage plays a central and complex role. In addition to its social role the minimum wage has been used as anti-inflationary policy, confirming its importance to the Brazilian Economy. This paper analyzes the effects of the minimum wage on both wages and employment using monthly household-level data (similar to the US CPS) over a reasonably long time period. A number of conceptual and identification questions is here discussed. Various strategies on how to best measure the effect of a constant (national) minimum wage are summarized in a “menu” of minimum wage variables. Also, an employment decomposition that separately estimates the hours worked and the number of jobs effects is used. Robust results indicate that an increase in the minimum wage strongly compresses the wages distribution with moderately small adverse effects on employment