冶炼方法和热处理工艺对0Cr12Mn5Ni4Mo3Al 高强不锈钢带力学性能和组织的影响

 研究了热处理对采用电炉+炉外精炼（LF）+电渣重熔冶炼的工业用和实验室50 kg真空感应炉+电渣重熔冶炼的试验用0Cr12Mn5Ni4Mo3Al高强度不锈钢带（0.8 mm和0.5 mm）的力学性能和组织的影响。结果表明,实验室得到的钢材更为洁净,组织中保留有合理的残余奥氏体含量;与采用同样热处理制度的工业钢带相比,在保持或提高伸长率的同时,抗拉强度提高50~85 MPa,杯突值提高1~3 mm;适当调节Cr、Ni的当量比以及采用合理的锻造、轧制工艺可以消除钢带组织中δ 铁素体的不利影响,更大限度发挥材料潜力。     

Residual stresses in high-velocity oxy-fuel metallic coatings

X-ray based residual stress measurements were made on type 316 stainless steel and Fe₃Al coatings that were high-velocity oxy-fuel (HVOF) sprayed onto low-carbon and stainless steel substrates. Nominal coating thicknesses varied from 250 to 1500 μm. The effect of HVOF spray particle velocity on residual stress and deposition efficiency was assessed by preparing coatings at three different torch chamber pressures. The effect of substrate thickness on residual stress was determined by spraying coatings onto thick (6.4 mm) and thin (1.4 mm) substrates. Residual stresses were compressive for both coating materials and increased in magnitude with spray velocity. For coatings applied to thick substrates, near-surface residual stresses were essentially constant with increasing coating thickness. Differences in thermal expansion coefficient between low-carbon and stainless steels led to a 180 MPa difference in residual stress for Fe₃Al coatings. Deposition efficiency for both materials is maximized at an intermediate (∼600 m/s) velocity. Considerations for X-ray measurement of residual stresses in HVOF coatings are also presented.     

Control of the mechanical properties of metal-ceramic interfaces through interfacial reactions

The use of interfacial reactions to control the structure and shear strength of metal-ceramic interfaces was studied in the NiO-Pt system. Interfaces were formed by hot1pressing together thin NiO single crystals and thick Pt polycrystalline films. Suitable choice of the annealing temperature, time and oxygen partial pressure allowed the introduction at the interface of a layer of either an intermetallic compound NiPt with thickness between 1 and 65 nm or a Ni-Pt solid solution.The shear strength of the NiO-Pt interface with and without the different interlayers present was measured by the periodic cracking method. Compared to its originally hot pressed state the shear strength of the NiO-Pt interface was increased by a factor of at least 4 by the presence of the NiPt and by ∼10 by the solid solution. The use of interfacial reactions to control interfacial strength may also be applicable in other metal-ceramic systems where the metal and the cation form intermetallic compounds, and where the oxidation potentials of the metal and the cation are significantly different.     

Posterior corneal surface topographic changes after laser in situ keratomileusis are related to residual corneal bed thickness

OBJECTIVE: To determine whether ectasia after laser in situ keratomileusis (LASIK) is related to residual corneal bed thickness. DESIGN: Retrospective noncomparative case series. PARTICIPANTS: Thirty-two eyes of 16 patients with refractive errors of -4.00 to -18.00 diopters were examined. INTERVENTION: LASIK was performed. The topography of the posterior corneal surface was examined with the Orbscan slit scanning corneal topography/pachymetry system. MAIN OUTCOME MEASURES: The difference in the elevation of posterior corneal surface regarding the best-fit sphere was measured. RESULTS: After surgery, mean bulge of 17.2 +/- 7.2 microns was found in eyes with residual corneal bed of 250 microns or greater, whereas 41.0 +/- 22.1 microns was seen in eyes with bed thickness less than 250 microns (t = 4.29; P = 0.000). CONCLUSION: Posterior corneal bulge is correlated with the residual corneal bed thickness. The risk of ectasia may be increased if the residual corneal bed is thinner than 250 microns.     

The role of the N-methyl-D-aspartic acid receptor in the relaxant effect of ketamine on tracheal smooth muscle

Ketamine and magnesium (Mg2+), well known bronchodilators, have been used to treat patients with status asthmaticus. Both can block the N-methyl-D-aspartic acid (NMDA) receptor. NMDA receptors exist in the airway, and their activation seems to be linked to the release actions of sensory neuropeptides resulting in increased airway tone. We sought to determine whether ketamine relaxes the guinea pig trachea contracted by histamine by blocking the NMDA receptor. Female guinea pigs (250-400 g) were killed with an overdose of pentobarbital. The trachea was removed and cut spirally into strips 3 mm wide and 15 mm long. The strips were mounted in a 10-mL organ bath filled with Tyrode's solution bubbled through with 95% O2/5% CO2 at 37 degrees C. Strip contractions were measured isometrically with a force displacement transducer. We then studied the effect of NMDA receptor antagonists on histamine-induced tracheal contraction. In this protocol, we examined the effect of ketamine, Mg2+, zinc (Zn2+), or MK-801 (a noncompetitive NMDA receptor blocker) on strips contracted by 10(-5) M histamine. After full contraction was attained, ketamine (0.5-1.5 mM), MgSO4 (2-8 mM), ZnCl2(0.2-0.8 mM), or MK-801 (1.5-6 x 10(-5) M) was added, and the strip tension was measured again. We also studied the effect of NMDA on the relaxation by ketamine. After full contraction by 10(-5) M histamine, 0.5-1.5 mM KET was added alone or in combination with 0.1 mM NMDA, and the strip tension was measured again. Finally, we measured the effect of MK-801 on the relaxant effect of ketamine. After full contraction by 10(-5) M histamine, 0.5-2 mM ketamine was added alone or in combination with 0.75 or 1.5 x 10(-5) M MK-801, and the strip tension was measured again. All NMDA receptor antagonists tested reversed the tracheal contraction induced by histamine in a dose-dependent manner. However, neither the agonist NMDA nor the noncompetitive receptor blocker MK-801 affected tracheal relaxation induced by ketamine. We conclude that ketamine relaxes the tracheal smooth muscle contracted by histamine through a mechanism independent of NMDA receptors. The decreased bronchomotor tone induced by ketamine is probably due to interference with a Ca2+-requiring step necessary to maintain the contraction caused by histamine. IMPLICATIONS: Stimulation of the N-methyl-D-aspartic acid (NMDA) receptor in the airway results in airway constriction. The bronchodilator ketamine blocks the NMDA receptor. However, ketamine relaxes the guinea pig trachea contracted by histamine through a mechanism independent of the NMDA receptor.     

Laser skin resurfacing. Er:YAG laser and cw-CO2 laser with scanner system in direct comparison]

PURPOSE: To integrate a newly developed OLCR instrument into the optical system of the excimer laser. The instrument is designed to perform corneal pachymetry before, during, and after corneal photoablation and thus allow for a precise and continuous on-line measurement of the corneal photoablation process. METHODS: The conditions required to integrate the OLCR instrument into the excimer laser optics were investigated. With a technical setting providing on-line data of corneal thickness, three groups of 8-10 corneae received central keratectomies of 27 (group 1), 82 (group 2) and 163 (group 3) microns calculated central depth and 7.38 mm diameter. All measurements were performed with OLCR and ultrasound. RESULTS: The OLCR instrument was coupled into the optical system of the excimer laser and a useful signal obtained at SLD power levels of 40 microW incident on the cornea. Individual corneal thickness measurements were obtained before, during and after the photoablation procedure. In group 1, the ablation was 50.3 (40-68) microns measured with ultrasound and 30.2 (27-38) microns measured with OLCR. In group 2, the ablation was 101.1 (80-113) microns measured with ultrasound and 93.3 (76-109) microns measured with OLCR. In group 3, the ablation was 210.6 (190-227) microns measured with ultrasound and 188.4 (181-197) microns measured with OLCR. The precision (standard deviation) for measurements of individual corneas was 1-2 microns with OLCR and up to 12 mm in Ultrasound measurements. CONCLUSION: With this interferometric method, continuous, non-contact measurement of corneal thickness before, during and after excimer laser photoablation were performed. By establishing a feed-back control between the pachymetric measurements and the photoablation process, the precision of excimer ablation may possibly be further increased.     

Dislocation mechanisms for the relaxation of thermal stress at metal-ceramic interfaces

Thermal stresses in the vicinity of the interface between metal and ceramic components result from the difference in the thermal expansion coefficients between the two materials when the temperature is changed. The dislocation structure in and near NiOPt interfaces that survived large temperature changes was studied in order to understand how a metal-ceramic couple accomodates thermal stresses that frequently can exceed the yield stress of the metal and the fracture stress of the ceramic. The interface structure for the exact (001) epitaxial orientation relationship between Pt and NiO is a square grid of misfit dislocations. A larger misfit dislocation spacing is expected to be present at room temperature than at the high temperature used during hot pressing to form the metal-ceramic bond. A dislocation mechanism based on climb and glide was suggested to produce this change of spacing and relieve the thermal stress. Experimental observations were obtained which are consistent with this mechanism.     

Effects of beta-adrenergic blockers on retinal circulation

We evaluated the effects of 0.5% betaxolol hydrochloride and 0.5% timolol maleate on retinal blood flow. We measured the diameter of the retinal artery (Da) and vein (Dv), and retinal venous blood flow rate (V) in 8 healthy young volunteers by laser speckle velocimetry before and after the application of betaxolol or timolol topically to both eyes daily for one week. There were no any significant changes. Da before and after the application of betaxolol was 114.2 +/- 6.3 (mean +/- standard deviation) microns and 115.6 +/- 6.7 microns and before and after the application of timolol, 117.5 +/- 12.7 microns and 101.3 +/- 9.5 microns. Dv before and after the application of betaxolol was 149.5 +/- 11.1 microns and 148.4 +/- 13.3 microns, and before and after the application of timolol 148.5 +/- 9.2 microns and 146.2 +/- 10.3 microns. V before and after the application of timolol was 12.3 +/- 2.6 mm/s and 12.6 +/- 2.4 mm/s, and before and after the application of betaxolol, 11.6 +/- 1.5 mm/s and 11.4 +/- 2.1 mm/s. Thus one-week application of the beta-blockers, betaxolol and timolol did not change the retinal arterial or venous blood flow.     

Polymerization contraction stress in thin resin composite layers as a function of layer thickness

OBJECTIVES: In the present study, the effect of layer thickness on the curing stress in thin resin composite layers was investigated. Since the value of the contraction stress is dependent on the compliance of the measuring equipment (especially for thin films), a method to determine the compliance of the test apparatus was tested. METHODS: A chemically initiated resin composite (Clearfil F2, Kuraray) was inserted between two sandblasted and silane-coated stainless steel discs in a tensilometer. The curing contraction of the cylindrical samples was continuously counteracted by feedback displacement of the tensilometer crosshead, and the curing stress development was registered. After 20 min, the samples were loaded in tension until fracture. The curing stress was determined for layer thicknesses of 50, 100, 200, 300, 400, 500, 600, 700 microns, 1.4 mm and 2.7 mm. The compliance of the apparatus was calculated with the aid of a non-linear regression analysis, using an equation derived from Hooke's Law as the model. RESULTS: None of the samples fractured due to contraction stress prior to tensile loading. The contraction stress after 20 min decreased from 23.3 +/- 5.3 MPa for the 50 microns layer to 5.5 +/- 0.6 MPa for the 2.7 mm layer. The compliance on the apparatus was 0.029 mm/MPa. SIGNIFICANCE: A measuring method was developed which was found to be suitable for the determination of axial polymerization contraction stress in this films of chemically initiated resin composites. The method makes it possible to estimate the stress levels that occur in resin composite films in the clinical situation.     

低压等离子喷涂耐高温涂层残余应力检测及分析

采用低压等离子工艺制备耐高温可磨耗涂层,通过光学显微镜观察了耐高温涂层的显微结构,采用逐层法与曲率法相结合的检测技术,对不同厚度涂层残余应力进行检测,形成了涂层厚度与残余应力分布及趋势图,运用热处理技术控制和消除涂层内部残余的涂层应力。结果表明,低压等离子喷涂的耐高温涂层表面残余应力随着涂层厚度的增加而增大,当涂层厚度达到0.6mm左右极限时,涂层会发生自然开裂,采用热处理的工艺方法可以减少涂层内的热应力导致的涂层残余应力。     

Fracture mechanics studies of thermal mismatch using a four-point bending specimen

Layered composites develop thermal residual stresses during cooling from processing temperature to room temperature. The thermal stresses reduce fracture toughness data measured in four-point bending tests. To obtain a material parameter characterizing the interface fracture toughness the measured data must be corrected for the influence of thermal stresses. Thermal stresses often lead to kinking of an interface crack out of its initial plane. This tendency can be quantified by two parameters: (i) the ratio G/G₀ of the energy release rate of the kinked crack G and the energy release rate of the interface crack G_O and (ii) the ratio of the local stress intensity factors at the tip of the interface crack, K_II/K_I. Both quantities have been computed for a variety of material combinations using the finite element method. They are found to be strongly affected by thermal and elastic mismatch. Fracture experiments have been performed using brittle glass/glass composites with different thermal mismatched. The obtained fracture toughness values and crack deflection angles have evaluated on the basis of the numerical results. Measured and calculated kinking angles are in excellent agreement. The contribution of residual thermal stresses to the interface fracture toughness K_c has been elaborated.     

高炉炉缸凝铁层导热系数测定及传热模型修正

摘要：高炉炉缸内衬表面形成稳定的凝铁层将延长高炉寿命。采用自制的凝铁层模拟实验装置，在中温高压条件下利用锡与焦炭制备凝铁层模拟样品；通过三维数码显微镜观察统计不同凝铁层模拟样品对应的金属与焦炭的面积比，采用瞬态平面热源法测定导热系数，探究其对凝铁层导热系数的影响。结果表明，凝铁层模拟样品（凝锡层）的导热系数范围是23.58～40.39W/（m·K）；凝铁层样品的导热系数范围为28.05～48.19W/（m·K）；还原凝铁层真实导热系数后，可以确定高炉炉缸区域传热模型中的气隙厚度为0.5～1.0mm。     

Influence of pipe processing on the mechanical properties of K60 steel sheet

The mechanical properties of thick steel sheet (13?C27 mm) produced at PAO MK Azovstal?? and the basic metal in K60 pipe (diameter 1220 mm) for the VSTO pipeline manufactured at PAO Khartsyzskii Trubnyi Zavod are subjected to statistical analysis, so as to establish the variation in the mechanical properties of the steel as a function of the sheet thickness and the wall thickness of the pipe and also under the influence of pipe processing.     

In-Situ Load Testing of Corrugated Steel Pipe-Arch Culverts

A large number of corrugated metal pipe-arch culverts are located under highways. This study investigates the field performance of four existing pipe-arch culverts under static and dynamic loads. Effects of various parameters were considered in selection of the culverts, including backfill height, loading conditions, age of placement, and culvert geometry. Static loads were applied at ten different locations above each culvert using heavily loaded test trucks. Six dynamic tests were conducted at speeds varying from 8 to 64?km/h. A portable instrumentation frame was installed inside each test culvert to monitor the deflections at five critical locations. During each test, strains were also measured using 14 strain gauges. Test results indicated that culvert response was influenced significantly by the backfill height. Nearly symmetrical deflection patterns were recorded for symmetrical loading about the longitudinal vertical plane through the crown. The maximum static deflections were larger than the maximum dynamic deflections for each culvert.     

Use of neutron and synchrotron X-ray diffraction for evaluation of residual stresses in a 2024-T351 aluminum alloy variable-polarity plasma-arc weld

The residual stress fields associated with variable-polarity plasma-arc (VPPA) welds in 2024-T351 aluminum alloy plates have been measured nondestructively using neutron and synchrotron X-ray diffraction. Neutron diffraction allows in-depth measurements of the full strain tensor to be made in thick components; synchrotron X-rays allow for rapid measurements of strains inside components, although their penetration is less than that of the neutrons and constraints arising from the diffraction geometry generally lead to only two strain components being easily measurable. Hence, a combination of the two techniques, applied as described herein, is ideal for a detailed nondestructive evaluation of residual stresses in plates. The residual stresses in a 12-mm-thick VPPA-welded aluminum 2024-T351 alloy plate have been measured using neutron diffraction. The stresses were then remeasured by a combination of neutron and synchrotron X-ray diffraction after the plate had been reduced in thickness (or, skimmed) to 7 mm by machining both sides of the weld, mimicking the likely manufacturing operation, should such welds be used in aerospace structures. A strong tensile residual stress field was measured in the longitudinal direction, parallel to the weld, in both the as-welded and skimmed specimens. There was only a slight modification of the residual stress state on skimming.     

Instrumentation of the patellar osteotomy in total knee arthroplasty. The relationship of patellar thickness and lateral retinacular release

This study investigates the influence of patellar thickness in total knee arthroplasty (TKA) with routine patellar resurfacing on the rate of lateral retinacular release. A study group comprised of 121 TKAs using surgical instrumentation allowing a measured resection of the patella was compared with a control group comprised of 100 TKAs using an "eye-ball" technique for patellar resurfacing without particular attention to patellar thickness. A composite without patellar thickness equal to or slightly less than the original patella was attempted in the study group. The average thickness difference of the patella in the study group was -1.58 mm. Lateral retinacular release for patellar maltracking was performed in 12.4% of knees in the study group compared with 55% of knees in the control group. The variation in patellar thickness in this series often led to a residual bone thickness < 15 mm. No clinical problems have been observed to date.     

In situ formation of metal-ceramic microstructures,including metal-ceramic composites,using reduction reactions

Partial reduction reactions were used to form a metallic phase either around or inside oxide grains in polycrystals in the FeMnO system. By suitable choice of oxide composition, partial pressure of oxygen, annealing time and temperature, it is possible to control the nucleation and growth of the metallic phase to produce a wide range of metal-ceramic microstructures. These include ceramic grains with a thin layer of metallic phase at their boundaries; ceramic grains with a thick layer of metallic phase at their boundaries —essentially, a metal-ceramic composite; and ceramic grains containing a fine distribution of metal particles—essentially, a ductile phase toughened ceramic. The presence of the metallic phase increases the fracture toughness of all the metal-ceramic microstructures with respect to that of the pure ceramic, with the largest increase observed for the metal-ceramic composite. It is believed that the principles established by studying the FeMnO system can be used on more practical mixed oxide systems to produce metal-ceramic microstructures, which in some cases are unique, and in particular, if the starting oxide material is in the form of plate- or rod-shaped crystals, to produce metal-ceramic composites in situ.     

Probabilistic Models of Damaging Deflections for Floor Elements

In this paper a number of serviceability issues related mainly to excessive deflections of structural floor elements (beams and slabs) are discussed. Field data of serviceability damage caused by excessive deflections of structural floor elements have been collected from various sources and probabilistic models are developed. Current serviceability specifications for allowable deflection limits in Australian, U.S., and other concrete structure codes have been compared against these probabilistic distributions of damaging deflections. Preliminary results confirm that allowable deflection limits in these design codes represent realistic lower-bound values of damaging deflections.     

Sarcocystis buffalonis n.sp. (Protozoa: Sarcocystidae) from the water buffalo (Bubalus bubalis) in Vietnam

Sarcocystis buffalonis n. sp. is proposed for a species forming thick-walled, macroscopic sarcocysts in skeletal muscles and the esophagus of the water buffalo (Bubalus bubalis). Sarcocysts of S. buffalonis were found in 68 (10.5%) of 647 buffalo carcasses examined grossly at slaughter in Ho Chi Minh City in southern Vietnam. Sarcocystis buffalonis sarcocysts were 1-8 mm long and 0.1-0.5 mm wide. The cyst wall was 3-7.7 microns thick and had palisadelike villar protrusions that were constricted at the base, expanded laterally in the mid-region, and tapered distally. The villar protrusions contained microfilaments and electron-dense granules. Sarcocysts of Sarcocystis fusiformis, the other well-known macroscopic species occurring in water buffalo, were also found in 60 of the 68 animals infected with S. buffalonis. Sarcocysts of S. fusiformis were thin walled and had characteristic cauliflowerlike villar protrusions. Two of 7 cats fed isolated S. buffalonis sarcocysts were found to have 12 x 8 microns sporocysts in their intestine or feces 10 days after inoculation.     

镁合金板带铸轧技术与进展

镁合金板材的应用需求正在扩大,而板带连续铸轧一直被认为是制造镁合金薄板的一种最有效的生产方式。通过综合回顾镁合金板材轧制技术和板材铸轧技术的发展与现状,分析讨论各种连续铸轧和半固态铸轧的工艺技术特点及其优缺点,并介绍了镁合金板带铸轧的新技术发展动向以及金属强制均匀化理论技术在铸轧镁合金薄板中的优越性和适用性。实验结果表明,金属熔体强制均匀化处理和加工成形可有效增加均质熔体的形核率,对合金凝固组织的均匀化、细化效果显著。