Rod Section Research Articles

Design and Optimization of Molecular Nanovalves Based on Redox-Switchable Bistable Rotaxanes

Redox-controllable molecular nanovalves based on mesoporous silica nanoparticles have been fabricated, using two bistable [2]rotaxanes with different spacer lengths between their recognition sites as the gatekeepers. Three different linkers with varying chain lengths have been employed to attach the bistable [2]rotaxane molecules covalently to the silica substrate. These nanovalves can be classified as having IN or OUT locations, based on the positions of the tethered bistable [2]rotaxanes with respect to the entrances to the nanopores. The nanovalves are more efficient when the bistable [2]rotaxane-based gatekeepers are anchored deep within (IN) the pores than when they are attached closer to (OUT) the pores' orifices. The silica nanopores can be closed and opened by moving the mechanically interlocked ring component of the bistable [2]rotaxane closer to and away from the pores' orifices, respectively, a process which allows luminescent probe molecules, such as coumarins, tris(2-phenylpyridine)iridium, and rhodamine B, to be loaded into or released from the mesoporous silica substrate on demand. The lengths of the linkers between the surface and the rotaxane molecules also play a critical role in determining the effectiveness of the nanovalves. The shorter the linkers, the less leaky are the nanovalves. However, the distance between the recognition units on the rod section of the rotaxane molecules does not have any significant influence on the nanovalves' leakiness. The controlled release of the probe molecules was investigated by measuring their luminescence intensities in response to ascorbic acid, which induces the ring's movement away from the pores' orifices, and consequently opens the nanovalves.

Research on Genetic Optimization of Special Spiral Rod Grinding Process

In the grinding process of special spiral rods, the actual feed rate is far below the allowable limit, resulting in great efficiency waste. To tackle the problem, this paper presents a controlling strategy which significantly improves rough grinding efficiency through changing grinding feed rate, enhances work-piece surface quality and shortens the processing time. Based on the establishment of the work cycle model of the special spiral rod grinding process, the strategy sets the grinding efficiency of each individual rod section as the objective function, thus via genetic algorithm realizes an optimal calculation on grinding feed rate variable and resolves the power and roundness constraint problem. Through computer simulation, an optimal grinding control plan is obtained which can help the grinding process to achieve overall optimization.

Material flow during the extrusion of simple and complex cross-sections using FEM

This paper deals with the extrusion of rod and shape sections and uses a 3D finite element model analysis (FEM) to predict the effect of die geometry on maximum extrusion load. A description of material flow in the container is considered in more detail for rod and shape sections in order to fully comprehend the transient conditions occurring during the process cycle. A comparison with experiments is made to assess the relative importance of some extrusion parameters in the extrusion process and to ensure that the numerical discretisation yields a realistic simulation of the process. The usefulness and the limitation of FEM are discussed when modelling complex shapes. Results are presented for velocity contours and shear stress distribution during the extrusion process. It is shown that for most of the shapes investigated, the material making up the extrudate cross-sections originates from differing regions of virgin material within the billet. The outside surface of the extrudate originates from the material moving along the dead metal zone (DMZ) and the core of the extrudate from the central deformation zone. The FE program appears to predict all the major characteristics of the flow observed macroscopically.

Shape and Phase Control of Colloidal ZnSe Nanocrystals

Shape- and phase-controlled ZnSe nanocrystals are synthesized in hot mixtures of long-chain alkylamines and alkylphosphines. The variation in the rate of precursor addition, down to low and controlled levels, allows the nucleation, as well as the growth of the nanocrystals, to switch between the wurtzite and the zinc blend structures. Such a level of control leads to a variety of shapes, from spheres to rods to three-dimensional structures formed by rod sections interconnected through branching points. The temperature- and time-dependence of the chemical potentials for the monomer species in solution are the most relevant parameters involved in the growth mechanism.

Honing Up a Genre of Amphiphilic Bistable [2]Rotaxanes for Device Settings

AbstractIn response to molecular electroactive device requirements, a molecular shuttle in the shape of an amphiphilic bistable [2]rotaxane has been designed, synthesized, and characterized. It contains a hydrophobic, tetraarylmethane and a hydrophilic, dendritic stopper and two π‐electron‐rich stations—a (monopyrrolo)tetrathiafulvalene unit and a 1,5‐dioxynaphthalene moiety — on the rod section of its dumbbell component, which can act as recognition sites for the tetracationic cyclophane, cyclobis(paraquat‐p‐phenylene), to reside around. In contrast to a previously reported “slow” amphiphilic bistable [2]rotaxane, which has an SMe group attached directly to the (monopyrrolo)tetrathiafulvalene unit, this “new and improved” bistable [2]rotaxane has a much less bulky hydrogen atom attached to the (monopyrrolo)tetrathiafulvalene unit. This seemingly small difference in the substituents on the (monopyrrolo)tetrathiafulvalene unit leads to profound changes when comparing the physical properties of the two bistable [2]rotaxanes. Two hydrophilic semidumbbell compounds, comprising only a (monopyrrolo)tetrathiafulvalene unit, and one hydrophobic semidumbbell compound comprising only a 1,5‐dioxynaphthalene moiety on its rod section have also been prepared and used to form their corresponding cyclobis(paraquat‐p‐phenylene) complexes. The kinetics of the complexation/decomplexation process occurring in these complexes have been investigated, using both absorption and 1H NMR spectroscopy. In addition, these model complexes have been used to investigate the strength of the noncovalent bonding interactions occurring between the cyclobis(paraquat‐p‐phenylene) ring component and the semidumbbell component at different temperatures, allowing the free energies, enthalpies, and entropies for the formation of these complexes to be determined. The outcome of these investigations can be used to explain the fact that the “slow” [2]rotaxane exists as a 1:1 mixture of its two possible translational isomers, whereas the “new and improved” [2]rotaxane exists as a 4:1 mixture in favor of the translational isomer where the cyclobis(paraquat‐p‐phenylene) tetracation encircles the (monopyrrolo)tetrathiafulvalene unit, and also to explain the thermochromic behavior of the “new and improved” [2]rotaxane. In this amphiphilic bistable [2]rotaxane, shuttling of the cyclobis(paraquat‐p‐phenylene) tetracation can be driven by both chemical and electrochemical oxidation of the (monopyrrolo)tetrathiafulvalene unit rendering it a good candidate for incorporation into two‐terminal molecular switch tunnel junctions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Controllable Donor–Acceptor Neutral [2]Rotaxanes

In pursuit of a neutral bistable [2]rotaxane made up of two tetraarylmethane stoppers--both carrying one isopropyl and two tert-butyl groups located at the para positions on each of three of the four aryl rings--known to permit the slippage of the pi-electron-donating 1,5-dinaphtho[38]crown-10 (1/5DNP38C10) at the thermodynamic instigation of pi-electron-accepting recognition sites, in this case, pyromellitic diimide (PmI) and 1,4,5,8-naphthalenetetracarboxylate diimide (NpI) units separated from each other along the rod section of the rotaxane's dumbbell component, and from the para positions of the fourth aryl group of the two stoppers by pentamethylene chains, a modular approach was employed in the synthesis of the dumbbell-shaped compound NpPmD, as well as of its two degenerate counterparts, one (PmPmD) which contains two PmI units and the other (NpNpD) which contains two NpI units. The bistable [2]rotaxane NpPmR, as well as its two degenerate analogues PmPmR and NpNpR, were obtained from the corresponding dumbbell-shaped compounds NpPmD, PmPmD, and NpNpD and 1/5DNP38C10 by slippage. Dynamic 1H NMR spectroscopy in CD2Cl2 revealed that shuttling of the 1/5DNP38C10 ring occurs in NpNpR and PmPmR, with activation barriers of 277 K of 14.0 and 10.9 kcal mol(-1), respectively, reflecting a much more pronounced donor-acceptor stabilizing interaction involving the NpI units over the PmI ones. The photophysical and electrochemical properties of the three neutral [2]rotaxanes and their dumbbell-shaped precursors have also been investigated in CH2Cl2. Interactions between 1/5DNP38C10 and PmI and NpI units located within the rod section of the dumbbell components of the [2]rotaxane give rise to the appearance of charge-transfer bands, the energies of which correlate with the electron-accepting properties of the two diimide moieties. Comparison between the positions of the visible absorption bands in the three [2]rotaxanes shows that, in NpPmR, the major translational isomer is the one in which 1/5DNP38C10 encircles the NpI unit. Correlations of the reduction potentials for all the compounds studied confirm that, in this non-degenerate [2]rotaxane, one of the translational isomers predominates. Furthermore, after deactivation of the NpI unit by one-electron reduction, the 1/5DNP38C10 macrocycle moves to the PmI unit. Li+ ions have been found to strengthen the interaction between the electron-donating crown ether and the electron-accepting diimide units, particularly the PmI one. Titration experiments show that two Li+ ions are involved in the strengthening of the donor-acceptor interaction. Addition of Li+ ions to NpPmR induces the 1/5DNP38C10 macrocycle to move from the NpI to the PmI unit. The Li+-ion-promoted switching of NpPmR in a 4:1 mixture of CD2Cl2 and CD3COCD3 has also been shown by 1H NMR spectroscopy to involve the mechanical movement of the 1/5DNP38C10 macrocycle from the NpI to the PmI unit, a process that can be reversed by adding an excess of [12]crown-4 to sequester the Li+ ions.

Switchable neutral bistable rotaxanes.

Two switchable neutral bistable [2]rotaxanes have been synthesized, and their chemically induced mechanical switching has been studied in solution by 1H NMR spectroscopy. One of the rotaxanes was prepared by a thermodynamically controlled slippage mechanism, while the other rotaxane was obtained by a dynamic covalent chemistry protocol involving the assembly of its dumbbell component by olefin metathesis. The recognition sites present in the rod section of the dumbbell component, namely, naphthodiimide (NpI) and pyromellitic diimide (PmI) residues, were chosen in the knowledge that the ring component, 1,5-dinaphtho[38]crown-10 (1/5DNP38C10), will bind preferentially to the NpI site. However, upon introduction of Li+ ions into the solution, a 1:2 complex is formed between the PmI site, encircled by the 1/5DNP38C10 ring and two Li+ ions. Since this complex is more stable overall than the binding between the 1/5DNP38C10 ring and the NpI site, the ring component moves from the NpI site to the PmI one. This mechanical movement can be reversed by adding an excess of [12]crown-4 to the solution to act as a sequestering agent for the Li+ ions.

Testing with SHPB from quasi-static to dynamic strain rates

We have developed a new method for separating dispersive waves in elastic and viscoelastic rods from three-point strain and one-point velocity measurements. Stress, strain, displacement and velocity, which were supposed to be homogenous in a rod section, were therefore determined at any point of the bar. This method is based on the assumption of a one dimensional and single mode dispersive wave propagation. This method was used in the frequency domain and took into account wave dispersion. It was shown to be stable with respect to noise. The measuring time is increased considerably. Subsequently, the maximum strain which can be measured in a material tested with a classical SHPB (Split Hopinson Pressure Bar) set-up is also increased and is no more limited by the length of the bars. The method was used to evaluate the rate sensitivity of a luminum honecomb over a wide range of strain-rates (from 10 -2 to 1000 s -1 ).

Amphiphilic Bistable Rotaxanes

AbstractTwo molecular shuttles/switches—a slow one and a fast one—in the shape of amphiphilic, bistable [2]rotaxanes have been synthesized and characterized. Both [2]rotaxanes contain a hydrophobic, tetraarylmethane and a hydrophilic, dendritic stopper. They are comprised of two π‐electron‐rich stations—a monopyrrolotetrathiafulvalene unit and a 1,5‐dioxynaphthalene moiety—which can act as recognition sites for the tetracationic cyclophane, cyclobis(paraquat‐p‐phenylene), to reside around. In addition, a model [2]rotaxane, incorporating only a monopyrrolotetrathiafulvalene unit in the rod section of the amphiphilic dumbbell component and cyclobis(paraquat‐p‐phenylene) as the ring component, has been investigated. The dumbbell‐shaped components were constructed using conventional synthetic methodologies to assemble 1) the hydrophobic, tetraarylmethane stopper and 2) the hydrophilic, dendritic stopper. Next, 3) the hydrophobic stopper was fused to the 1,5‐dioxynaphthalene moiety and/or the monopyrrolotetrathiafulvalene unit by appropriate alkylations, followed by 4) attachment of the hydrophilic stopper, once again by alkylation to give the dumbbell‐shaped compounds. Finally, 5) the [2]rotaxanes were self‐assembled by using the dumbbells as templates for the formation of the encircling cyclobis(paraquat‐p‐phenylene) tetracations. The two [2]rotaxanes differ in their arrangement of the π‐electron‐rich units, one in which the SMe group of the monopyrrolotetrathiafulvalene unit points toward the 1,5‐dioxynaphthalene moiety (2⋅4 PF6) and another in which it points away from the 1,5‐dioxynaphthalene moiety (3⋅4 PF6). This seemingly small difference in the orientation of the monopyrrolotetrathiafulvalene unit leads to profound changes in the physical properties of these rotaxanes. The bistable [2]rotaxanes were both isolated as brown solids. 1H NMR and UV‐visible spectroscopy, and electrochemical investigations, reveal the presence of both possible translational isomers at ambient temperature. As a consequence of the existence of both possible translational isomers in these bistable [2]rotaxanes, they exhibit a complex electrochemical behavior, which is further complicated by the presence of folded conformations wherein the monopyrrolotetrathiafulvalene unit is involved in an “alongside” interaction with the tetracationic cyclophane. In the molecular shuttle/switch 2⋅4 PF6 a “knob”, in the shape of the SMe group, is situated between the monopyrrolotetrathiafulvalene and the 1,5‐dioxynaphthalene recognition sites, making it possible to isolate both translational isomers (2⋅4 PF6⋅GREEN and 2⋅4 PF6⋅RED) and to investigate the kinetics of the shuttling of the cyclobis(paraquat‐p‐phenylene) tetracation between the two recognition sites. The shuttling processes, which are accompanied by clearly detectable color changes, can be followed by 1H NMR and UV‐visible spectroscopy, allowing the rate constants and energies of activation for the translation of the cyclobis(paraquat‐p‐phenylene) tetracations between the two recognition sites to be determined. In the molecular shuttle/switch 3⋅4 PF6, there is no “knob” situated between the 1,5‐dioxynaphthalene and the monopyrrolotetrathiafulvalene recognition sites, resulting in a considerably faster shuttling of the cyclobis(paraquat‐p‐phenylene) tetracation between these two sites, making the separation of the two possible translational isomers of 3⋅4 PF6 impractical. However, the shuttling of the cyclobis(paraquat‐p‐phenylene) tetracation can be followed by dynamic 1H NMR spectroscopy. At low temperatures, the major translational isomer is 3⋅4 PF6⋅RED, while 3⋅4 PF6⋅GREEN is the major isomer at higher temperature. In the bistable [2]rotaxanes shuttling of the cyclobis(paraquat‐p‐phenylene) tetracations can be driven by electrochemical oxidation of the monopyrrolotetrathiafulvalene unit. In complexes in which one of the two dumbbell stoppers is missing, electrochemical oxidation causes dethreading.

ICONE11-36613 BEHAVIOR OF STEELS IN FLOWING LIQUID PB/BI AT 420-600℃ AFTER 4000-7200 H

Corrosion tests were carried out on austenitic AISI 316L and 1.4970 steel and on martensitic MANET 10Cr steel in flowing (up to 1.3 m/s) Pb/Bi. The concentration of oxygen in the liquid alloy was controlled at (10)^<-6> wt%. Specimens consisted of tube and rod sections in original state and after alloying of Al into the surface. Martensitic steels develop thick protective magnetite and spinel layers that spall off and grow again during long term exposure (7200 h). At 600℃ the oxide scale changes to thin protective spinel layers with partial dissolution attack at some spots. Austenitic steels exhibit thin spinel layers at 420℃ and thick spinel and magnetite layers at 550℃ which are protective. The spinel layer is also replaced after it brakes off. Severe attack of the liquid alloy occurs on austenite at 600℃ already in the 2000 h exposure period. Steels with 8 - 15 wt% Al alloyed into the surface suffer no corrosion attack at all experimental temperatures and exposure times.

ＭｇＢ２超電導線の交流通電における自己磁界損失

The measurement and analysis of AC transport current loss (self-field loss) in MgB2 superconducting composites were studied. In experimental results, the normalized Ic dependency of AC loss in the MgB2 deviated from Norris' theoretical curve. Then a numerical analysis was performed by taking into consideration the model of a round superconducting wire that consisted of three concentric layers. The analysis clearly showed the experimentally obtained results, such as that the phenomenon originated in the inhomogeneity of the critical current density in the wire rod section.

A Puff-by-Puff Delivery Model for Cigarettes

Abstract Materials generated by combustion and pyrolysis in a lit cigarette move through the tobacco rod and filter sections in two phases, the particulate phase and the gas phase. Some particles are removed while moving through the rod and filter sections. The gas-phase materials include the vapor of many volatile compounds. While moving through the rod and filter sections, part of the vapor are removed by adsorption and condensation. In this study, a puff-by-puff delivery model for cigarettes is developed to calculate “tar”, water, and nicotine in smoke on a puff-by-puff basis. A number of parameters can be obtained by the best fit to the experimental results of some cigarettes with different filter lengths. The parameters include the materials generated at the coal for each puff, the particle and vapor removal constants for tobacco rods and filters. The parameters may be useful in understanding some characteristics of cigarette smoke.

Interfacial segregation of Ti in the brazing of diamond grits onto a steel substrate using a Cu-Sn-Ti brazing alloy

Diamond grits were brazed onto a steel substrate using a prealloyed Cu-10Sn-15Ti (wt pct) brazing alloy at 925 °C and 1050 °C. Due to the relatively high concentration of Ti in the brazing alloy, the braze matrix exhibited a composite structure, composed of β-(Cu,Sn), a Cu-based solid solution, and various intermetallic compounds with different morphologies. The reaction of Ti with diamond yielded a continuous TiC layer on the surfaces of the diamond grits. On top of the TiC growth front, an intermetallic compound, composed of Sn and Ti, nucleated and grew into a randomly interwoven fine lacey structure. An interfacial structure developed as the interwoven fine lacey phase was semicoherently bonded to the TiC layer, with the Cu-based braze matrix filling its interstices. The thickness of such a composite layer was increased linearly with the square root of isothermal holding time at 925 °C, complying with the law of a diffusion-controlled process. However, at 1050 °C, the segregation behavior of Ti and Sn to the interfaces between the TiC layer and the braze matrix diminished, due to the increased solubility of Ti in the Cu-based liquid phase. The enhanced dissolution of Ti in the Cu-based liquid phase at 1050 °C also caused the precipitation of rod-like CuTi with an average diameter of about 0.2 µm during cooling. SnTi3 was the predominant intermetallic compound and existed in three different forms in the braze matrix. It existed as interconnected grains of large size which either floated to the surface of the braze matrix or grew into faceted grains. It also exhibited a nail-like structure with a mean diameter of about 1 µm for the rod section and a lamellar structure arising from a eutectic reaction during cooling.

Reversing a rotaxane recognition motif: threading oligoethylene glycol derivatives through a dicationic cyclophane.

An already well-established recognition motif-namely one in which the NH2+ centers in the rod sections of the dumbbell components of rotaxanes are encircled by macrocyclic polyether components-has been turned simultaneously outside-in and inside-out, a fact that has been proved beyond any doubt by the stoppering of both ends of a [2]pseudorotaxane to give a stable [2]rotaxane. The [2]pseudorotaxane is formed in nitromethane when a benzylic dibromide, obtained after reacting an excess of 1,4-bis(bromomethyl)benzene with hexaethylene glycol, is added to an equimolar amount of a dicationic cyclophane in which two -CH2OCH2- chains link a pair of dibenzylammonium ions through the para positions on their phenyl rings. When the [2]pseudorotaxane is reacted in nitromethane with triphenylphosphine, a [2]rotaxane and the corresponding free dumbbell compound are isolated in 58 and 31% yields, respectively. The structure of the [2]rotaxane is established by using mass spectrometry (FABMS and ESMS) and NMR (1H and 13C) spectroscopy in nitromethane-d3. The [2]rotaxane exhibits quite dramatic changes in the 1H chemical shifts of the signals for its CH2N+ and CH2O protons compared with those in the free dumbbell compound. The 1H NMR spectrum of the [2]pseudorotaxane shows many similar features. Titration experiments with three of the six different CH2O probes give an average Ka value of 2900 +/- 750 M-1 in nitromethane-d3. The new recognition motif for the template-directed synthesis of rotaxanes can now be exploited at both the molecular and macromolecular levels of structure with numerous potential applications in sight.

Results of steel corrosion tests in flowing liquid Pb/Bi at 420–600 °C after 2000 h

Corrosion tests were carried out on austenitic AISI 316L and 1.4970 steels and on MANET steel up to 2000 h of exposure to flowing (up to 2 m/s) Pb/Bi. The concentration of oxygen in the liquid alloy was controlled at 10 −6 wt%. Specimens consisted of tube and rod sections in original state and after alloying of Al into the surface. After 2000 h of exposure at 420 and 550 °C the specimen surfaces were covered with an intact oxide layer which provided a good protection against corrosion attack of the liquid Pb/Bi alloy. After the same time corrosion attack at 600 °C was severe at the original AISI 316L steel specimens. The alloyed specimens containing FeAl on the surface of the alloyed layer still maintained an intact oxide layer with good corrosion protection up to 600 °C.

Diode-pumped regenerative amplifier delivering 100-mJ single-mode laser pulses

We report on a side-pumped Nd:phosphate laser regenerative amplifier that delivers laser pulses of as much as 100 mJ in a single TEM mode. The laser beam is mode matched to the amplification medium by an intracavity fused-silica phase plate for mode shaping and a telescope for adjustment of the beam mode to the amplification rod section such that most of the energy stored in the rod is transferred to the laser pulses. As a result of the good overlap and the low loss, an optical-to-optical conversion efficiency of as much as 10% was measured for a pumping current of 80 A and greater than 100-mJ output pulses.

Longitudinal vibrations of elastic rods of stepwise-variable cross-section colliding with a rigid obstacle

A frequency method of solving the problem of the longitudinal vibrations of elastic rods of stepwise-variable cross-section is proposed, taking into account or ignoring the energy dissipation when they collide with a rigid obstacle. A Laplace transformation is applied to the equation of longitudinal vibrations of the rod when there are non-zero initial conditions. For the inhomogeneous differential equation obtained, the boundary-value problem of finding the Laplace-transformed longitudinal boundary forces as functions of the boundary displacements is solved. The equations of equilibrium of the junction points, which are a system of equations for the unknown junction displacements, are then set up. Since the corresponding coefficients are obtained by exact integration, there is no constraint on the length of the rod sections. An inverse transformation is carried out by using extremal points of the amplitude-phase frequency characteristics [1] or by direct integration. A rod of constant cross-section of finite length is considered as a test example. The result is compared with the well-known wave solution [2]. The proposed approach is described here for the first time and imposes practically no constraints on the class of problems that can be considered, whereas the existing approach leads to unsurmountable difficulties when there are several sections of the rod.

Self-assembly of an amphiphilic

The template-directed synthesis of a [2]rotaxane, in which a pi-electron deficient ring component-cyclobis(paraquat-p-phenylene)-is assembled around a pi-electron rich asymmetric monopyrrolotetrathiafulvalene unit on the rod section of an amphiphilic dumbbell component that is terminated by a hydrophilic dendritic stopper at one end and a hydrophobic tetraarylmethane stopper at the other end, is reported.

The Kern of a Stretched Section is the Stretched Kern of the Section

We are concerned with a rod subjected to an axial force not acting through the centroid of the rod section. Suppose the kern shape of the section is known. Now suppose we have another rod section which is derived from the first by ‘stretching’ it along a principal axis. We show that the kern of the derived section is gotten by stretching the original kern to the same degree as the section was stretched.

Propagation of small surface cracks in stainless steel at high temperature : Chen, J. and Takezono, S. Engineering Fracture Mechanics (1996) 54, 751–759

This paper presents the results of a failure analysis investigation conducted in a connecting rod from a diesel engine used in the generation of electrical energy. The investigation included an extensive analysis of the con-rod material as well as the fracture zone. The investigation involved the following experimental procedures and testing techniques: visual inspection, fractography, magnetic particle inspection, chemical analysis, tensile and hardness testing, metallography, and microanalysis. The connecting rod was fabricated from an AISI/SAE 4140 low alloy steel; chemical composition, mechanical properties and microstructure were appropriate for the application. The connecting rod fractured at the body in a section close to the head; the origin of the fracture was located at the con-rod lubrication channel. The lubrication channel exhibited an area containing a tungsten based material, presumably from a machining tool, embedded in its surface as a result of a deficient manufacturing process. This area acted as nucleation site for cracks that propagate through the connecting rod section by a fatigue mechanism, reducing its section and finally producing its catastrophic failure.