How transition paths differ:enterprise performance in Russia and China

We use enterprise survey data to analyse and contrast the determinants of enterprise performance in China and Russia. We find that in China, enterprise growth and efficiency is associated with rapid increases in factor inputs, and with ownership to a lesser extent, but not greatly correlated with industry-specific or institutional factors. However, in Russia, enterprise growth is not associated with improvements in factor quantity (except for labor) or quality. The main determinants of company performance are instead demand and institutional factors at a regional level. The findings are robust across a variety of specifications.

Paths of the least resistance:understanding how motives form in international retail joint venturing

Developing the premise that strategies are forged through an ongoing mutual process of developing motives and responses to multiple degrees of resistance, this paper examines the motives underpinning the adoption of joint venture strategies using empirical details from four British retail firms. The findings point to multiple motives forming from multiple paths of resistance in the foreign market, but also among individuals within the firm as well as across the whole international programme. Moreover, this study reveals a paradoxical tension between management's operational impatience to immediately ground the retail format and an overall wariness or gloomy perceptions associated with adopting an international retail joint venture. The paper therefore concludes that the motives and barriers are manifestations of the struggles involved in internationalising retail operations.

Competition for shortest paths on sparse graphs

Optimal paths connecting randomly selected network nodes and fixed routers are studied analytically in the presence of a nonlinear overlap cost that penalizes congestion. Routing becomes more difficult as the number of selected nodes increases and exhibits ergodicity breaking in the case of multiple routers. The ground state of such systems reveals nonmonotonic complex behaviors in average path length and algorithmic convergence, depending on the network topology, and densities of communicating nodes and routers. A distributed linearly scalable routing algorithm is also devised. © 2012 American Physical Society.

H-induced platelet and crack formation in hydrogenated epitaxial Si/Si0.98 B0.02 /Si structures

An approach to transfer a high-quality Si layer for the fabrication of silicon-on-insulator wafers has been proposed based on the investigation of platelet and crack formation in hydrogenated epitaxialSi/Si0.98B0.02/Si structures grown by molecular-beam epitaxy. H-related defect formation during hydrogenation was found to be very sensitive to the thickness of the buried Si0.98B0.02 layer. For hydrogenated Si containing a 130nm thick Si0.98B0.02 layer, no platelets or cracking were observed in the B-doped region. Upon reducing the thickness of the buried Si0.98B0.02 layer to 3nm, localized continuous cracking was observed along the interface between the Si and the B-doped layers. In the latter case, the strains at the interface are believed to facilitate the (100)-oriented platelet formation and (100)-oriented crack propagation.

The effect of frequency and microstructure on corrosion fatigue crack propagation in high strength aluminium alloys

Fatigue crack growth in high strength aluminium alloy 7150 commercial plate material has been studied in both laboratory air and acidified aqueous salt solution. The aggressive aqueous environment enhanced fatigue crack growth rates by up to an order in magnitude compared to laboratory air. The enhancement in fatigue crack growth rate was accompanied by evidence of embrittlement in the crack path, involving both brittle intergranular and transgranular failure modes. Both the enhancement of fatigue crack growth rates and the extent of intergranular growth modes are dependent on cyclic frequency which, along with the absence of a similar frequency effect in a spray-formed version of the material with a significantly different grain structure, supports a mechanism of grain boundary hydrogen diffusion for intergranular corrosion fatigue crack growth. The convergence of corrosion fatigue crack growth rates at high ΔK in both spray-formed and conventional plate materials coincides with the operation of identical transgranular corrosion fatigue modes dependent on strain-controlled hydrogen diffusion ahead of the crack tip. © 1997 Acta Metallurgica Inc.

Effect of thermal residual stresses on fatigue crack opening and propagation behavior in an Al/SiCp metal matrix composite

The effects of a thermal residual stress field on fatigue crack growth in a silicon carbide particle-reinforced aluminum alloy have been measured. Stress fields were introduced into plates of material by means of a quench from a solution heat-treatment temperature. Measurements using neutron diffraction have shown that this introduces an approximately parabolic stress field into the plates, varying from compressive at the surfaces to tensile in the center. Long fatigue cracks were grown in specimens cut from as-quenched plates and in specimens which were given a stress-relieving overaging heat treatment prior to testing. Crack closure levels for these cracks were determined as a function of the position of the crack tip in the residual stress field, and these are shown to differ between as-quenched and stress-relieved samples. By monitoring the compliance of the specimens during fatigue cycling, the degree to which the residual stresses close the crack has been evaluated. © 1995 The Minerals, Metals & Material Society.

Role of reinforcement/matrix interfacial strength in fatigue crack propagation in particulate SiC reinforced aluminum alloy 8090

A study has been made of the influence of the reinforcement/matrix interfacial strength on fatigue crack propagation in a powder metallurgy aluminum alloy 8090-SiC particulate composite. The interfacial region has been altered by two separate routes, the first involving aging of the 8090 matrix, with the subsequent formation of precipitate free zones at the boundaries, and the second consisting of oxidizing the surface of the SiC particles before their incorporation into the composite. In the naturally aged condition, oxidation of the SiC leads to a reduction in fatigue crack growth resistance at higher values of stress intensity range ΔK. This is due to a proportion of the crack growth occurring through voids formed in association with many of the weak SiC interfaces which have retained a layer of thick surface oxide after processing. On overaging no difference in crack growth rate is discernible between the oxidized and unoxidized SiC composites. It is proposed that this is due to similar levels of interfacial weakening having occurred in both composites, indicating that this is an important factor in the reduction of the high ΔK crack growth resistance of the unoxidized SiC composite on aging.

Influence of macroscopic residual stress fields on fatigue crack growth measurement in SiC particulate reinforced 8090 aluminium alloy

The effect of residual stresses, induced by cold water quenching, on the morphology of fatigue crack fronts has been investigated in a powder metallurgy 8090 aluminium alloy, with and without reinforcement in the form of 20 wt-%SiC particles. Residual stress measurements reveal that the surface compressive stresses developed in these materials are significantly greater than in conventional metallurgy ingot 8090, because surface yielding occurs on quenching. The yield stresses of the powder route materials are greater than those of ingot produced 8090 and hence greater surface stresses can be maintained. In fatigue, severe crack front bowing is observed in the powder formed materials as a result of the reduction of the R ratio (minimum load/maximum load) by the compressive residual stresses at the sides of the specimen, causing premature crack closure and hence reducing the local driving force for fatigue crack growth ΔKeff. This distortion of the crack fronts introduces large errors into measurements of crack growth rate and threshold values of ΔK.

Fatigue crack propagation in nickel-base superalloys:effects of microstructure, load ratio, and temperature

The current state of knowledge and understanding of the long fatigue crack propagation behavior of nickel-base superalloys are reviewed, with particular emphasis on turbine disk materials. The data are presented in the form of crack growth rate versus stress intensity factor range curves, and the effects of such variables as microstructure, load ratio, and temperature in the near-threshold and Paris regimes of the curves, are discussed.

Microstructural and environmental effects on fatigue crack propagation in duplex stainless steels

Fatigue crack initiation and propagation in duplex stainless steels are strongly affected by microstructure in both inert and aggressive environments. Fatigue crack growth rates in wrought Zeron 100 duplex stainless steel in air were found to vary with orientation depending on the frequency of crack tip retardation at ferrite/austenite grain boundaries. Fatigue crack propagation rates in 3.5% NaCl solution and high purity water are increased by hydrogen assisted transgranular cyclic cleavage of the ferrite. The corrosion fatigue results are interpreted using a model for the cyclic cleavage mechanism.

Fatigue crack propagation mechanisms in a thermally aged duplex stainless steel

Zeron 100 duplex stainless steel is susceptible to embrittlement following ageing at temperatures between 350 °C and 450 °C. The embrittlement is associated with cleavage of the age-hardened ferrite phase, initiated by deformation twinning. This can result in order of magnitude increases in the fatigue crack propagation rate. The effects of ageing on the mechanisms of fatigue crack propagation in Zero 100 are investigated, and a quantitative model is developed, accounting for the effects of hardness, temperature, stress level and microstructure on the fatigue crack growth rate. © 1994.

Fatigue crack growth behaviour in molten-metal processed SiC particle-reinforced aluminium alloys

Fatigue crack initiation and subsequent short crack growth behaviour of 2014-5wt%SiC aluminium alloy composites has been examined in 4-point bend loading using smooth bar specimens. The growth rates of long fatigue cracks have also been measured at different stress ratios using pre-cracked specimens. The distributions of SiC particles and of coarse constituent particles in the matrix (which arise as a result of the molten-metal processing and relatively slow cooling rate) have been investigated. Preferential crack initiation sites were found to be SiC-matrix interfaces, SiC particles associated with constituent particles and the coarse constituent particles themselves. For microstructurally short cracks the dispersed SiC particles also act as temporary crack arresters. In the long crack growth tests, higher fatigue crack growth rates were obtained than for monolithic alloys. This effect is attributed to the contribution of void formation, due to the decohesion of SiC particles, to the fatigue crack growth process in the composite. Above crack depths of about 200 μm 'short' crack growth rates were in good agreement with the long crack data, showing a Pris exponent, m = 4 in both cases. For the long crack and short crack growth tests little effect of specimen orientation and grain size was observed on fatigue crack growth rates, but, specimen orientation affected the toughness. No effect of stress ratio in the range R = 0.2-0.5 was seen for long crack data in the Paris region.

Effects of dynamic strain ageing on fatigue crack propagation and threshold behaviour in a Ni-base superalloy

In the temperature range 200-400 degree C the Ni-base superalloy, N901, develops marked dynamic strain ageing effects in its tensile behavior. These include inverse strain rate sensitivity, especially in UTS values, strongly serrated stress-strain curves and a heavily sheared failure mode at the higher test-temperatures. As for steels these effects seem to be due to interactions between the dislocations and the interstitial carbon atoms present. The results of tensile and fatigue threshold tests carried out between 20 degree C and 420 degree C are reported and the fatigue behavior is discussed in terms of the effects of surface roughness induced closure, temperature and strain aging interactions.

Comparison of crack growth behaviour between spray-formed and commercial plate Al-Zn-Mg-Cu alloy 7150

This paper compares the crack growth resistance of an experimental spray-formed extrusion with that of a commercial aluminium alloy, the two alloys having similar compositions but markedly different grain structures. Tensile and fracture behaviour is similar in both materials and is influenced by inclusion content. The two materials differ in their crack growth resistance, which is shown to be dependent upon grain size and shape. Environmentally-induced crack growth is favoured by aligned grain boundaries and small grain size.

Crack closure and residual stress effects in fatigue of a particle-reinforced metal matrix composite

A study of the influence of macroscopic quenching stresses on long fatigue crack growth in an aluminium alloy-SiC composite has been made. Direct comparison between quenched plate, where high residual stresses are present, and quenched and stretched plate, where they have been eliminated, has highlighted their rôle in crack closure. Despite similar strength levels and identical crack growth mechanisms, the stretched composite displays faster crack growth rates over the complete range of ΔK, measured at R = 0.1, with threshold being displaced to a lower nominal ΔK value. Closure levels are dependent upon crack length, but are greater in the unstretched composite, due to the effect of surface compressive stresses acting to close the crack tip. These result in lower values of ΔKeff in the unstretched material, explaining the slower crack growth rates. Effective ΔKth values are measured at 1.7 MPa√m, confirmed by constant Kmax testing. In the absence of residual stress, closure levels of approximately 2.5 MPa√m are measured and this is attributed to a roughness mechanism.