NVH and reliability analyses of the engine with different interaction models between the crankshaft and bearing

The precision of the interaction model is very important to predict NVH and the reliability of an internal combustion engine. The interaction model between the crankshaft and the bearing is hard to be established precisely due to its complex interaction relationship and dynamic characteristic. In this paper, the elasto-hydrodynamic lubrication model with cavitation theory is built to couple with multi-body dynamic theory to analyze the noise and reliability of the engine, the results were compared with nonlinear spring model and hydrodynamic lubrication model based on a typical in-line six cylinder engines, such as load carrying capacity of the bearing, velocity level of the engine surface, noise level of engine surface and stress of the crankshaft. The results showed that the vibration, noise and stress prediction difference is due to the exciting of the oil film pressure distribution, rigid and flexible body that is used to build the dynamic model will lead the load capacity of the bearing to be great different. Nonlinear spring model and hydrodynamic lubrication model are precise enough to predict the vibration or noise. The All the analysis will provide the guidance for the engine NVH optimization and structural reliability design.     

Shape-memory materials as a working substance for martensitic rotary engines

A martensitic rotary engine has been designed. The physical properties of its working substance are studied, and the power characteristics of the engine are determined. Temperature and stress cycling are shown to adversely affect the properties of the working element (a coil spring made of titanium nickelide) and, thus, to decrease the engine efficiency.     

Incorporation of Benzocyclobutene Cross-Linkable Moieties in Poly(Methyl Acrylate): A Novel Approach to Shape-Memory Polymers Accompanied with Microphase Separation

Benzocyclobutene (BCB) moieties were incorporated into a typical polyolefin, poly(methyl acrylate), by free radical copolymerization of benzocyclobutene-4-yl acrylate and methyl acrylate. The subsequent cross-linking of the generated copolymers by ring-opening reaction of BCB gave rise to shape-memory polymers. This new cross-linking process did not require cross-linker and yielded small molecules. Most importantly, submicron-sized particles within the cross-linked polymers, which were observed using atomic force microscope, were induced by this cross-linking strategy. The results of the shape-memory tests suggested that the cross-linked polymers displayed good shape-memory performance.     

Catastrophic Fermi surface reconstruction in the shape-memory alloy AuZn

AuZn undergoes a shape-memory transition at 67 K. The de Haas-van Alphen effect persists to 100 K enabling the observation of a change in the quantum oscillation spectrum indicative of a catastrophic Fermi surface reconstruction at the transition. The coexistence of both Fermi surfaces at low temperatures suggests an intrinsic phase separation in the bulk of the material. In addition, Dingle analysis reveals a sharp change in the scattering mechanism at a threshold cyclotron radius, attributable to the underlying microstructure driving the shape-memory effect.     

铁电马氏体中的电致形状记忆效应

与温度驱动形状记忆的缓慢响应及磁场驱动形状记忆的巨大体积相比较，电场驱动形状记忆具有响应快和体积小的优点。但是，基于传统反压电效应的电场驱动形状记忆由于变形量较小而收到限制。本研究表明，通过运用基于点缺陷短程序对称性遵循的普适性原理的可逆畴翻转机制，可以在铁电马氏体中获得巨大的电致形状记忆效应；其产生的变形量理论上是反压电效应所产生变形量的几十倍。采用原位畴观察实验给出了可逆畴翻转的直接证据。并且，在铁电多晶陶瓷中也获得了这种大的电致形状记忆效应。这种效应在很宽的频率范围内都很稳定，在疲劳测试中也显示了很好的可靠性。运用这一新的电致形状效应有望制备出新一代非线性驱动器材料。     

Magnetic control of magnetic shape-memory single crystals

We present a phenomenological model for the magneto-mechanical evolution of shape-memory alloy single crystals. The existence of solutions for given magnetic field is commented and optimal control results are established.     

A SIMPLE MODEL TO ESTIMATE THE IMPACT FORCE INDUCED BY PISTON SLAP

The dynamics of piston's secondary motion (lateral and rotational motion) across the clearance between piston and cylinder inner wall of reciprocating machines are analyzed. This paper presents an analytical model, which can predict the impact forces and vibratory response of engine block surface induced by the piston slap of an internal combustion engine. A piston is modelled on a three-degree-of-freedom system to represent its planar motion. When slap occurs, the impact point between piston skirt and cylinder inner wall is modelled on a two-degree-of-freedom vibratory system. The equivalent parameters such as mass, spring constant, and damping constant of piston and cylinder inner wall are estimated by using measured (driving) point mobility. Those parameters are used to calculate the impact force and for estimating the vibration level of engine block surfaces. The predicted results are compared with experimental results to verify the model.     

Shape-memory effect in PMN-PT(65/35) ceramic

We report the observation of fairly large and fully recoverable shape-memory strain in thin bars of lead magnesium niobate lead titanate ceramic for a composition (65/35) near its morphotropic phase-boundary. The recoverable shape strain produced by bending and thermal-cycling experiments is ∼0.3%, similar in magnitude to that reported for the shape-memory effect (SME) observed in some other dielectric ceramics. An explanation of the observed SME and the recoverable shape-strain is given in terms of the ferroelastic phase transitions, and the availability of a large number of competing phases and domain states near the morphotropic phase boundary in this material. The stress-induced shifting of the temperatures at which the ferroelastic phase transitions occur also plays an important role in ensuring good crystallographic reversibility around the thermal-cycling experiments.     

Pseudoelastic deformation and generation of reactive stresses in a Cu-Al-Ni shape-memory alloy in the temperature range 4.2–293 K

Pseudoelastic deformation and the magnitude of reactive stresses in Cu-14.2% Al-4.5% Ni shape-memory alloy single crystals were studied experimentally in the temperature range 4.2–293 K. It is established that pseudoelasticity and the shape-memory effect are observed in this alloy over the entire temperature range indicated above. It is found that, as the constrained samples are heated at a constant rate from liquid-helium temperature, the reactive stresses increase continuously at temperatures of up to 100 K and then remain constant. When the temperature of preliminary deformation is 77 K, the generation of reactive stresses with an increase in temperature occurs by two stages, which agrees with the multistage behavior of the pseudoelastic-deformation curves of this alloy above the liquid-nitrogen boiling temperature. Using the theory of diffuse martensitic transitions, a quantitative calculation is performed of pseudoelastic-deformation curves and reactive-stress curves over the temperature range 4.2–293 K under conditions of two-stage behavior of the martensitic transformation.     

Microstructure of rapidly quenched nickel-enriched TiNi binary alloys in the initial state and after annealing

The microstructure of shape-memory melt-spun TiNi binary alloys of nonstoichiometric composition in the initial state and after annealing has been studied for the first time by transmission electron microscopy and X-ray diffraction in a wide temperature range.     

In situ synchrotron X-ray microdiffraction analysis of thermomechanically induced phase transformations in Cu–Al–Ni shape-memory alloy

Phase transformations in a single-crystal Cu–Al–Ni shape-memory alloy induced by thermomechanical effects were investigated in situ by high-resolution synchrotron X-ray microdiffraction. Contrary to the common belief, austenite texture maps revealed that austenite-to-martensite transformation occurred during heating of the partially transformed material under fixed specimen elongation. Twinned and detwinned types of martensite coexisted during this austenite-to-martensite phase transformation. Twinning and detwinning structures evolved to accommodate changes in stress and strain generated in the temperature-varying environment. Small amounts of austenite exhibiting distorted crystallographic orientation were detected in regions of stress-induced martensite during heating of the partially transformed material. The results of this investigation provide insight into intriguing stress rate-dependent phenomena intrinsic of shape-memory alloys and elucidate complex phase transformations due to thermal and mechanical stress effects.     

Texture development and deformation mechanisms during uniaxial straining of U–Nb shape-memory alloys

The shape-memory effect is well documented in uranium–niobium alloys near the α″–γ^o metastable phase boundary. In situ neutron diffraction measurements during uniaxial loading indicate that U–14?at.%?Nb (in the α″ monoclinic phase field) deforms by stress-induced twin reorientation. Alternatively, U–16?at.%?Nb (initially γ^o tetragonal) undergoes a stress-induced phase transformation to the α″ monoclinic phase. The crystallographic texture of the monoclinic phase of both compositions has been measured and qualitatively interpreted by considering the orientation relationship between the most favoured α′′ variant and the parent phase. In addition, previously published observations of deformation structures within the shape-memory regime of a U–13?at.%?Nb alloy are discussed within the context of the same model.     

Martensitic transformation in single-crystal Cu-Al-Ni shape-memory alloy under load: Visualization by photoacoustic microscopy

Photoacoustic microscopy is applied to observe the surface structure of Cu-Al-Ni shape-memory single crystals in both the loaded and unloaded state. Visualizing the early stages of the loading-induced martensitic transformation is demonstrated to be feasible. The photoacoustic images are distinguished to advantage from the corresponding CCD images by a higher contrast between different phases of the shape memory alloy.     

Rearrangement of crystallographic domains driven by magnetic field in antiferromagnetic CoO

The rearrangement was investigated of crystallographic domains in the antiferromagnetic pseudo-tetragonal phase in CoO (Néel temperature: 293 K) when the domains were driven by a magnetic field. A rearrangement is generally observed in ferromagnetic shape-memory alloys. The rearrangement was found to occur at temperatures between 170 K and 293 K, but not at temperatures below 170 K. In order to determine the reason for such a difference, the shear stress driven by a magnetic field, τ _mag, was calculated and compared with the shear stress required for twinning plane movement, τ _req. It was found that τ _mag is equal to or larger than τ _req whenever the rearrangement of crystallographic domains occurs due to the application of a magnetic field, and vice versa. This observation is similar to past observations in the case of many ferromagnetic shape-memory alloys.     

Influence of neutron irradiation on the martensitic transformations and shape-memory effect in a TiNi alloy

The paper reports measurements of the strains and electrical resistance of a TiNi shape-memory alloy under irradiation in the low-temperature helium circuit of a nuclear reactor. Irradiation of the alloy in martensitic state at 170 K revealed that the transition temperatures from cubic to rhombohedral and from rhombohedral to monoclinic phase decrease exponentially with increasing dose. No change in the shape-memory effects and transformation plasticity was observed up to a dose of 6.7×10²² n/m². Keeping the sample at 340 K without irradiation restores (increases) partially the transition temperatures. The relations observed can be assigned to a change in the degree of long-range order in the lattice caused by neutron irradiation. Fiz. Tverd. Tela (St. Petersburg) 40, 1705–1709 (September 1998)     

Ginzburg-Landau theory of static domain walls in shape-memory alloys

A one-dimensional static Ginzburg-Landau theory for the martensitic phase transitions in shape-memory alloys is developed. From the equilibrium conditions the structure of static domain walls of martensite-martensite as well as of martensite-austenite type is calculated. In the finite crystal a discrete spectrum of domain structures results whereas in an unbounded crystal there are four types of domain walls. For each type of walls the energy is calculated.     

Updating a software package for the simulation of diffraction patterns and the computation of the parameters of the twinning and self-accommodation of martensite crystals

An updated software package for the simulation of point diffraction pictures and the computation of several crystallographic characteristics of martensite crystals in alloys with the shape-memory effect is presented. Optimization was carried out for the procedure of the analysis of the orientation relationships between the lattices of austenite and martensite from the viewpoint of the possibility of the formation of self-accommodation complexes.     

Simulation of thermomechanical and electrothermal hysteresis phenomena in porous nickel titanium

There is represented a general scheme of functioning and the corresponding model of a porous biomicrofluid matrix based on nickel titanium, which possesses a shape-memory effect, prepared by the method of selective laser sintering. The simulation of thermomechanical and electrothermal hysteresis phenomena composes the basis of the functioning of this MEMS. Such a model can be used for estimating the efficiency and controllability of drug delivery systems via the change in the volume of pores.     

Two-way reversible deformation in titanium nickelide

A systematic study has been made of the shape-memory effects which arise in titanium nickelide after prestraining under isothermal conditions. It has been found that under thermal cycling in the free state a broad spectrum of phenomena is observed — repeatedly reversible shape memory, reversible deformation, deformation of an oriented transformation, etc., each of which can be realized independently of the others in the temperature range of the B2 R and R B19' transformations. When summing up the observed laws of the mechanical behavior of the material we used concepts of heterogeneous development of deformation in crystals, structurally hereditary properties of alloys with a shape-memory effect, as well as the principle of independent initiation of various channels of deformation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 71–76, August, 1988.     

High-pressure-induced baroelastic effects and martensitic transformations in two-layer micro-and nanocomposites

The theory of smeared diffusionless martensitic transitions is applied to analyzing martensitic transformation and relaxation of baroelastic stress in a thin shape-memory alloy layer included in a two-layer microcomposite. When omnidirectional pressure is applied to the composite, baroelastic stress arises in the alloy because of the different bulk compression moduli of the alloy and the substrate material. Baroelastic strain in the microcomposite undergoing martensitic transformation is found to acquire nonlinear and hysteretic properties, which can be used in pressure microtransducers and special-purpose miniature actuators.