Direct electroless Ni-P plating on AZ91D magnesium alloy

An electroless Ni-P plating treatment was applied on AZ91D magnesium alloy to improve its corrosion resistance. Optimum pretreatment conditions and optimum bath of electroless nickel plating for magnesium alloy were found through many experiments. In order to avoid bother of pre-plating medium layer, a set of procedure of direct electroless Ni-P under the acid condition was investigated. The properties of the coating with 10% phosphorus were investigated. The results show that a coating with high hardness, low porosity and good adhesive strength is obtained. X-ray diffraction patterns show that the structure of the coating is an amorphous phase. After annealing at 400℃, the amorphous phase of Ni-P is transformed to crystalline phases, and some intermetallics as Ni3P and Ni5P2 are deposited from Ni-P solid solution along with an enhancing hardness from Hv 450 to Hv 910.

High-temperature tribological properties of Ni-P alloy coatings deposited by electro-brush plating

High-temperature tribological properties of Ni-P alloy coatings processed by electro-brush plating on 20CrMo steel have been investigated. A baU-on-disc configuration was employed and 4 mm diameter Si3N4 balls were used as static counterpart. All the wear tests were carried out at 450℃ for 180 rain without lubricants. The electro-brush plating Ni-P coating is amorphous in as-deposited condition, and it becomes polycrystalline with the formation of Ni and Ni3P after heat treatment at 450℃for 1 h. The friction coefficient of the Ni-P coating is just 50% of that of the 20CrMo steel at the friction temperature of 450℃. A mild adhesive wear mechanism was found for the electro-brush plating Ni-P coating tested at 450℃, whereas for the 20CrMo steel at the same temperature a mixed adhesive and abrasive wear mechanism was observed.

ON THE ORIENTATION OF BUCKLING DIRECTION OF ANISOTROPIC ELASTIC PLATE UNDER UNIAXIAL COMPRESSION

The theory of small deformation superimposed on a largedeformation of an elastic solid is used to investigate the bucklingof anisotropic elastic plate under uniaxial compression. The bucklingdirec- tion (th direction of buckling direction is obtained. It isfound that the out-of-plane buckling of anisotropic elastic plate ispossible and both buckling conditions for flexural and extensionalmodes are presented.

Wear and Corrosion Resistance of Electroless Plating Ni-P Coating on P110 Steel

In order to improve the surface performance and increase the lifetime of P 110 oil casing tube steel during operation, electroless plating was conducted to form Ni-P coating onto its surface. The surface morphology/element distribution and phase constitution of the Ni-P coating were analyzed using scanning electron microscope （SEM） equipped with energy dispersive spectrometry （EDS） and X-ray diffraction （XRD）. Tribological and electrochemical measurement tests were applied to investigate the wear and corrosion resistance of P110 steel and the Ni-P coating. The results showed that a uniform and compact, high phosphorous Ni-P coating was formed. The obtained Ni-P coating indicated certain friction-reduction effect and lower mass loss during friction-wear tests. The Ni-P coating also exhibited higher corrosion resistance in comparison with bared P 110 steel. The obtained N i-P coating has significantly improved the surface performance of P110 steel.

Electrochemical behavior of Cu-Zn-Al shape memory alloy after surface modification by electroless plated Ni-P

The electrochemical behavior of Cu-Zn-Al shape memory alloy (SMA) with andwithout electroless plated Ni-P was investigated by electrochemical methods, in artificial Tyrode'ssolution. The results showed that Cu-Zn-Al SMA engendered dezincification corrosion in Tyrode'ssolution. The anodic active current densities as well as electrochemical dissolution sensitivity ofthe electroless plated Ni-P Cu-Zn-Al SMA increased with NaCl concentration rising, pH of solutiondecreasing and environmental temperature uprising. X-ray diffraction analysis indicated that aftersurface modification by electroless plated Ni-P, an amorphous plated film formed on the surface ofCu-Zn-Al SMA. This film can effectively isolate matrix metal from corrosion media and significantlyimprove the electrochemical property of Cu-Zn-Al SMA in artificial Tyrode's solution.

Investigation on a Non-cyanide Plating Process of Ni-P Coating on Magnesium Alloy AZ91D

In this research we presented a non-cyanide plating process of Ni-P alloy coating on Mg alloy AZ91D. By applying a new process flow of electroless nickel plating in which zinc coating is used as transition of Ni-P coating on Mg alloy AZ91D, the process of copper transition coating plated in the cyanides bath can be replaced. A new bath composed of NiSO4 was established by orthogonal test. The results show that zinc transition coating can increase the adhesion and protect the Mg alloy substrate from the bath corrosion. The optimal plating bath composition is NiSO4·6H2O 20 g/L, NaH2PO2·H2O20g/L and C6H8O7·H2O 2.5 g/L, and optimal bath acidity and optimal plating temperature are pH 4.0 and 95℃, respectively. The present process flow is composed of ultrasonic cleaning→alkaline cleaning→acid pickling→activation→double immersing zinc→electroplating zinc→electroless nickel plating→passivation treatment. The present non-cyanide process of electroless nickel plating is harmless to our surroundings and Ni-P coating on Mg alloy AZ91D produced by present process possesses good adhesion and corrosion resistance.

Insulin exerts direct, IGF-1 independent actions in growth plate chondrocytes

Insufficient insulin production or action in diabetic states is associated with growth retardation and impaired bone healing, while the underling mechanisms are unknown. In this study, we sought to define the role of insulin signaling in the growth plate. Insulin treatment of embryonic metatarsal bones from wild-type mice increased chondrocyte proliferation. Mice lacking insulin receptor （IR） selectively in chondrocytes （CartIR-/-） had no discernable differences in total femoral length compared to control littermates. However, CartIR-/- mice exhibited an increase in chondrocyte numbers in the growth plate than that of the controls. Chondrocytes lacking IR had elevated insulin-like growth factor （IGF）-IR mRNA and protein levels. Subsequently, IGF-1 induced phosphorylafion of Akt and ERK was enhanced, while this action was eliminated when the cells were treated with IGF-1R inhibitor Picropodophyllin. Deletion of the IR impaired chondrogenic differentiation, and the effect could not be restored by treatment of insulin, but partially rescued by IGF-1 treatment. Intriguingly, the size of hypertrophic chondrocytes was smaller in CartIR-/- mice when compared with that of the control littermates, which was associated with upregnlation of tuberous sclerosis complex 2 （TSC2）. These results suggest that deletion of the IR in chondrocytes sensitizes IGF-1R signaling and action, IR and IGF-1R coordinate to regulate the proliferation, differentiation and hypertrophy of growth plate chondrocytes.

Corrosion and wear properties of electroless Ni-P plating layer on AZ91D magnesium alloy

A direct electroless Ni-P plating treatment was applied to AZ91D magnesium alloy for improving its corrosion resistance and wear resistance. Corrosion resistance of the Ni-P coatings was evaluated by potentiodynamic polarization and immersing experiments in 3.5% NaCl solution. The wear resistance of the coatings was investigated by the wear track and the mass change after ball-on-disk experiment. The results show that corrosion resistance and wear resistance of the AZ91D alloy are greatly improved after direct electroless Ni-P plating. No discoloration is noticed until 4 d of immersion in 3.5% NaCl solution. Potentiodynamic polarization experiments show that the free corrosion potential of magnesium alloy is shifted from -1 500 mV to -250 mV and passivation occurs at 1 350 mV after direct electroless plating. The friction coefficients and wear rates of Ni-P coating and Ni-P coating after tempering are 0.10-0.351, 9.038×10-3 mm3/m and 0.13-0.177, 3.056×10-4 mm3/m, respectively, at a load of 1.5 N with dry sliding. Although minor hurt on corrosion resistance was caused, significant improvement of wear resistance was obtained after tempering treatment of the coating.

Three-dimensional free vibration analysis of multi-directional functionally graded piezoelectric annular plates on elastic foundations via state space based differential quadrature method

The three-dimensional free vibration analysis of a multi-directional func- tionally graded piezoelectric （FGP） annular plate resting on two parameter （Pasternak） elastic foundations is investigated under different boundary conditions. The material properties are assumed to vary continuously along the radial and thickness directions and have exponent-law distribution. A semi-analytical approach named the state space based differential quadrature method （SSDQM） is used to provide an analytical solution along the thickness using the state space method （SSM） and an approximate solution along the radial direction using the one-dimensional differential quadrature method （DQM）. The influence of the Winkler and shear stiffness of the foundation~ the material property graded variations, and the circumferential wave number on the nomdimensional natural frequency of multi-directional FGP annular plates is studied.

AXISYMMETRIC BENDING OF TWO-DIRECTIONAL FUNCTIONALLY GRADED CIRCULAR AND ANNULAR PLATES

Assuming the material properties varying with an exponential law both in the thick- ness and radial directions, axisymmetric bending of two-directional functionally graded circular and annular plates is studied using the semi-analytical numerical method in this paper. The deflections and stresses of the plates are presented. Numerical results show the well accuracy and convergence of the method. Compared with the finite element method, the semi-analytical nu- merical method is with great advantage in the computational efficiency. Moreover, study on ax- isymmetric bending of two-directional functionally graded annular plate shows that such plates have better performance than those made of isotropic homogeneous materials or one-directional functionally graded materials. Two-directional functionally graded material is a potential alternative to the one-directional functionally graded material. And the integrated design of materials and structures can really be achieved in two-directional functionally graded materials.

Thermal Effect on Vibration of Parallelogram Plate of Bi-Direction Linearly Varying Thickness

In this paper, the effect of thermal gradient on the vibration of parallelogram plate with linearly varying thickness in both direction having clamped boundary conditions on all the four edges is analyzed. Thermal effect on vibration of such plate has been taken as one-dimensional distribution in linear form only. An approximate but quiet convenient frequency equation is derived using Rayleigh-Ritz technique with a two-term deflection function. The frequencies corresponding to the first two modes of vibration of a clamped parallelogram plate have been computed for different values of aspect ratio, thermal gradient, taper constants and skew angle. The results have been presented in tabular forms. The results obtained in this study are reduced to that of unheated parallelogram plates of uniform thickness and have generally been compared with the published one.

不同界面下梁端直剪型锚栓钢板剪切承载力试验研究

开展梁端直剪型锚栓钢板剪切承载力加固试验研究。试验序列包含1个对比试验段、5个剪切承载力加固试验段。试验参数包括界面条件和钢板高度。结果表明:受力过程中钢板与混凝土之间的黏结界面终会剥离,不同黏结界面不影响剪切承载力;增加钢板高度和配套的直剪型锚栓数量能有效提高混凝土梁的剪切承载力。直剪型锚栓钢板剪切承载力加固存在2种机制,约束机制通过限制斜裂缝宽度提高剪切承载力,而组合受力机制通过钢板将一部分剪力直接传入支座。加固钢板高度较小时以约束机制为主,加固钢板高度较大时,2种加固机制联合发挥作用。

增材制造中空风冷板工艺设计与试验

为了验证增材制造技术对复杂中空风冷板的可行性,对中空风冷板模型增材制造工艺性、增材制造打印成型工艺性和粉末选择进行了分析对比。文中优选成熟AlSi10Mg铝合金打印参数完成中空风冷板的成型,并对随炉打印的试样力学性能和表面处理防护性能进行了试验验证。试验结果表明,增材中空风冷板性能可以满足产品设计使用要求。

铝基化学镀Ni-P前处理工艺对镀层结合力的影响

从原理及工艺条件的选择上对铝基化学镀Ni P的“二次浸锌法”、“预镀镍法”和“直接镀法”3种前处理工艺进行了较详细的讨论 ,同时分析了 3种前处理工艺对Ni P镀层与基体间结合强度的影响及原因。

镁合金化学镀Ni-P合金工艺研究

采用硫酸镍为主盐在AZ31D镁合金表面直接化学镀Ni-P合金,优化了工艺条件,讨论了镀液pH、施镀温度、主盐、次磷酸钠及柠檬酸等因素对化学镀Ni-P合金的影响,利用金相显微镜等对镀层进行了测试。结果表明所得镀层光滑、致密、均匀,耐蚀性较好。

镁合金直接化学镀Ni-P合金工艺

研究了镁合金经酸洗直接进行化学镀Ni-P合金工艺。用金相显微镜及扫描电子显微镜观察了镁合金表面经不同时间酸洗后的表面形貌及对镀层质量的影响。分析了镀液pH、温度对镀速的影响,并测试了镀层的表面形貌和耐蚀性。当酸洗时间为25 s时,所得到的镀层均匀致密,结合力好,耐蚀性能大大提高。

浸镀时间对镀钯无氧铜线镀层质量的影响

采用直接镀法和扫描电子显微镜研究了影响无氧铜线镀钯层质量的因素。结果表明:浸镀时间和纳米钯粉含量对无氧铜线镀钯层质量有显著影响。当镀液中纳米钯粉的质量分数为2%、表面活性剂OP-10的质量分数为3%时,在室温浸镀15 min以上的无氧铜线表面纳米钯颗粒团聚较少,几乎无露铜现象;纳米钯粉和OP-10的质量分数分别增加至4%和6%时,在室温浸镀20 min的无氧铜线镀层质量最好。此外,当镀液温度升高至约60℃时,浸镀15 min的无氧铜线镀层不均匀,漏铜现象明显。在450℃真空退火后,镀钯铜线的镀层界面结合强度和平整度提高。

镁合金表面Ni-P-纳米SiC复合化学镀层的耐腐蚀性能

为了提高AZ91D镁合金的应用性能,将纳米SiC引入Ni-P镀液,采用化学镀的方法制备了Ni-P-纳米SiC复合镀层,研究了Ni-P-纳米SiC镀层的孔隙率、盐雾性能以及阳极极化曲线,并与Ni-P化学镀层的耐蚀性进行了对比。结果表明:Ni-P-纳米SiC镀层均匀、致密,纳米SiC在镀层表面呈弥散分布;当纳米SiC浓度为4g/L时,复合镀层的孔隙率最小,为1个/cm,耐蚀时间(90h)明显长于Ni-P镀层(60h),腐蚀电位为-0.58V,略高于Ni-P镀层(-0.59V)。

玉米锥形脱粒装置仿真优化设计

我国北方地区常用的玉米籽粒直收收获机在脱粒工序中存在脱粒元件对果穗冲击强度过大的问题,为此设计一种低损高效的玉米锥形脱粒分离装置。对脱粒滚筒结构进行分析,建立果穗与脱粒凹板间的接触模型,确定滚筒最优参数的取值范围。通过EDEM软件对不同参数组合的脱粒分离装置进行仿真优化试验。结果表明,当脱粒滚筒锥角为8°,凹板选用左向圆管型结构,滚筒转速为400 r/min时,脱粒效果最佳,并与传统式脱粒滚筒相比,起脱段脱粒元件对果穗的碰撞力由284 N降低为234 N,碰撞反力由202.54 N降低为171.52 N,从而验证锥形脱粒滚筒具有降低对果穗冲击强度的特性。利用ADAMS软件对锥形脱粒装置进行运动学及动平衡仿真分析,验证研究成果的可靠性及理论可行性,且系统产生的不平衡惯性力符合农业机械设计要求。为后续玉米脱粒分离装置的创新设计和结构改进提供理论参考。

A TIME DOMAIN METHOD FOR QUASI-STATIC ANALYSIS OF VISCOELASTIC THIN PLATES

Based on the Boltzmann’s superposition principles of linear viscoelastic materials and the von K*-rm*-n’s hypotheses of thin plates with large deflections, a mathematical model for quasi-static problems of viscoelastic thin plates was given. By the Galerkin method in spatial domain, the original integro-partial-differential system could be transformed into an integral system. The latter further was reduced to a differential system by using the new method for temporal domain presented in this paper. Numerical results show that compared with the ordinary finite difference method, the new method in this paper is simpler to operate and has some advantages, such as, no storage and quicker computational speed etc.