渐开线圆柱齿轮齿廓偏差的分析与检测

积极采用齿轮国际标准,采用先进的加工工艺,如精滚工艺、修磨齿形及改变刀具材料实现硬齿面剃齿等,使齿轮制造质量批量、稳定地达到标准要求,是我国重要的技术经济政策。新近颁布的GB／T 10095．1—2001《渐开线圆柱齿轮 精度 第1部分     

圆弧齿圆柱蜗杆副轮齿强度分析

介绍圆弧齿圆柱蜗杆副齿廓啮合原理,齿形车削加工方法,建立起GB9147—88圆弧齿圆柱蜗杆副蜗轮、蜗杆的有限元计算模型。分析蜗轮蜗杆啮合过程中2个特殊承载位置应力与位移的变化,用动力学理论计算出蜗杆传动固有频率、临界转速,为试制GB9147—88圆弧圆柱蜗杆减速器提供合理而可靠的理论依据。     

齿轮接触强度的研究及基于Visual Basic语言的程序设计

根据齿轮啮合原理和接触力学,深入研究了渐开线齿轮传动啮合过程中各啮合点的接触应力计算,研究了不同参数齿轮传动最大接触应力可能出现的啮合位置,分析了国家标准(GB/T 3480-1997)接触强度计算公式,指出了国家标准中接触应力计算公式的局限性,提出了更加全面的确定和计算最大接触应力的方法;并运用Visual Basic语言和Microsoft Visual Basic6.0软件,编制了齿轮接触强度的计算程序;程序为计算齿轮的几何参数、接触应力及接触强度校核提供了快捷的工具,可以大大提高了齿轮设计的效率.     

渐开线齿轮单齿啮合区的齿形系数

本文对范成法加工的渐开线圆柱齿轮，在单对齿啮合受载时，按轮齿危险截面形状（分平截面法和折截面法）、加工方法（分齿条刀类和插齿刀类），给出四组齿形系数的计算式。此式既可计算标准（或非标准）齿轮齿顶受载时的齿形系数，又可计算标准（或非标准）齿轮齿廓任意点受载时的齿形系数，还可计算具有非标准齿廓参数的渐开线齿轮任意点受载的齿形系数，为精确计算轮齿齿根弯曲强度提供了依据。     

标准圆柱齿轮设计中齿数的一种确定方法

介绍了一种等强度设计下标准圆柱齿轮齿数的计算方法,使得齿轮设计中的齿数初选量化,进而达到简化设计步骤、优化设计结果、改善齿轮传动啮合质量的目的。     

Experimental simulator of outer-space conditions for the study of friction and wear

The operating conditions of movable couples and friction units in outer space are considered. The main factors affecting the friction and wear of materials in the outer-space environment are determined. An experimental simulator is described for studying outer-space friction interactions under terrestrial conditions.     

Determining the impact pulse at the point of tooth engagement in the driving and driven gears of a transmission

The impact pulse and speeds of the driving and driven gears in the transmission after impact at the point of engagement are determined.     

The development of Ferrography as a laboratory wear measurement method for the study of engine operating conditions on diesel engine wear

Ferrographic oil analysis techniques were used in a laboratory study of diesel engine wear. Data were developed supporting the concept of using the Severity Index I_s to rank the effect of engine operating conditions on wear. Results analyzing the Severity Index as a function of time and as a function of engine operating variables are presented. The Severity Index is also linearly correlated to spectrometric data (iron and lead concentrations in the used oil samples). Engine wear tends to increase with increase of either oil or coolant temperature. However, brake specific fuel consumption tends to decrease as oil and coolant temperatures increase, indicating a need for accurate temperature control for both mediums to minimize fuel consumption and wear. The heated Ferrogram analysis (HFA) technique was used to determine changes in the wear rates of specific engine parts with variation of the oil and coolant temperatures.     

A corrected assessment of the cylindrical shell finite element of bogner, fox and schmit when applied to arches

Previous work of the authors contained a mistaken assessment of the cylindrical shell finite element of Bogner, Fox and Schmit. The present note gives a corrected assessment.     

A semi-analytical technique for bending analysis of cylindrical panels with general loading and boundary conditions

Cylindrical panels are structural elements widely used in engineering structures for high value of strength to weight ratio. Exact solutions of cylindrical panels are available only for a very limited number of cases. The main target of this paper is to utilize a semianalytical technique to study bending behavior of cylindrical panels with different boundary conditions under general distributed loading. The solution of the partial differential equations was reduced to an iterative sequential solution of a double set of ordinary differential equations using extended Kantorovich method. The competence and accuracy of the method is established by comparison with available results in the literature and finite element analyses which shows good agreement.     

The effect of microstructure and wear conditions on the wear resistance of steel metal matrix composites fabricated with PTA alloying technique

The concept of hard particles in a softer metal matrix has long appealed to number of industries dealing among others with drilling and mining. For these facilities, the PTA (Plasma Transferred Arc) alloying technique is advisable and advantageous for several reasons; the equipment may be portable and moved near the working site, the treatment may be applied strictly to the area where the wear problem is situated and after the treatment little machining is required. Four different coatings are tested against three different modes of wear occurring either alone or less frequently combined in this kind of applications, i.e. adhesion, low stress abrasion and two-body abrasion. Two of the coatings examined belong to the category of tool steels with very hard carbides in their microstructure, namely TiC, M₂C and M₆C. The other two are boride coatings belonging to the Fe–B and Fe–Cr–B system respectively. A heat treated AISI D2 tool steel commonly used in this type of applications is also examined for comparison. Fe–Cr–B coating performance is at least 2 times better in low stress and two-body abrasion and four orders of magnitude better in adhesion wear than the AISI D2 tool steel. Fe–B coating can be used in pure adhesion or abrasion situations, but their brittleness forbids their use in situations involving impact loading. AISI M2 coating presents similar wear performance with AISI D2 tool steel in abrasion, whereas in adhesion wear it performs at least two orders of magnitude better. MMC–TiC coating has good performance in pure two-body abrasion situations due to the presence of the very hard TiC particles in its microstructure.     

Using a corrected least-squares procedure and accounting for structural parameters when analyzing the correlation between the impact strength of low-alloyed steels and their coercive force

The use of a corrected least-squares procedure that takes the error of impact-strength estimation into account, as well as several structure parameters, such as the equiaxial grain size number, Widmanstätten ferrite grain size number, and bainite percentage, allowed us to substantially improve the constraint equations between the impact strength and coercive force for a group of specimens. These specimens were sampled from no. 60 flange beams made of 09Г2 steel and exhibited no preliminary correlation between these parameters.     

A technique for forecasting the durability of rolling bearings and the optimum choice of lubricants under flood-lubrication and oil-starvation conditions

Effective conditions of friction in units that ensure performance and maximum longevity have been created by flood lubrication under the conditions of elastohydrodynamic (EHD) lubrication. In connection with this, prolonging the service life of friction units by ensuring local requirements to the amount of oil in the contact area and establishing the optimum choice of lubricating material in terms of its viscosity ratings is a topical problem for rolling bearings. Thus, it is suggested to determine the parameter of the lubricating layer (λ) values for the conditions of flood lubrication (λ_o) and progressing (λ_o.s ) and catastrophic (λ _c.s ) oil starvation for a wide spectrum of lubricating materials of different viscosity, since, in oil starvation mode, the efficiency of EHD conditions is violated, the lubrication mode is disturbed, and the bearing capacity of the EHD lubricating layer is lost.     

Evaluation of braze bonded hard complex boride based coatings for sliding,erosion and abrasion wear

Materials requiring improved resistance to wear have been researched in coatings as well as in bulk form. A new process that aims to produce a wear resistant surface through powder metallurgy exists. The process brazes a green tape containing a reactive mixture of Mo, Fe, Cr, MoB and FeB and which produces a microstructure of hard complex borides dispersed in a soft metallic matrix, onto a compatible metallic substrate. Hence the process is called as “Braze-bonding”. In the process the phenomena of coating densification, microstructure development and interface development occur simultaneously. The resultant hard layer is evaluated for performance under sliding wear, erosive wear and abrasive wear conditions. It has been found that the coating is competitive to other hard materials. The process has inherent advantages like applying the coating in situ and easily allows for varying the thickness of the coated layer. A diffusion driven interface between coating and substrate improves bond strength. Complex borides of more than 50 vol.% dispersed in a Fe based ductile matrix help in abating wear through different mechanisms, which have been discussed here. The braze coatings can be used for applications involving wear resistance like pump impeller parts, machining tools, and injection molding screws.     

Evaluation of roughness, hardness, and strength of AA 6061 molds for manufacturing polymeric microdevices

In the manufacturing of polymeric microfluidic devices, micro-molds play a key role because they determine not only the manufacturing cost but also the quality of the molded parts. Recently, a high-quality aluminum alloy 6061 (AA6061) mold with fine features less than its grain size has been fabricated economically by a hot embossing technique. However, temperature cycling during hot embossing process in mold manufacturing reduces significantly the original tensile strength and hardness of the AA6061-T6 alloy substrate, which is not desirable. In this study, a tempering process is carried out to recover the tensile strength and hardness of the embossed mold. To evaluate the changes of these properties, surface roughness, tensile strength, and hardness values were measured in each stage: (1) before hot embossing, (2) after hot embossing, and (3) tempering to T4 and tempering to T6. The results obtained demonstrate that the original strengths and hardness can be fully recovered by a post-tempering process after hot embossing, but with an increase in surface roughness. Moreover, accelerated testing was carried out to evaluate the changes in hardness and roughness of AA6061-T4 and T6 molds under the typical hot embossing temperature cycles of manufacturing polymeric devices. The results obtained indicate that these temperature cycles have only a minor effect on the roughness of both T4 and T6 molds and will increase the hardness of T4 molds to T6 temper, and have negligible effect on the hardness of a T6 temper mold.     

ADRC-PID cascade control method for a vehicle mounted and unbalanced barrel pitching system under the conditions of bumpy road and erosion wear

The barrel pitching system (BPS) is a typical electro-hydraulic servo control system. In actual service, the primary control difficulty is how to effectively restrain the influence of the barrel’s unbalanced torque (UT) and bumpy road (BR). Furthermore, with the extension of service life, the gradual depletion behavior, such as erosion wear (EW), will induce the core parameter’s decay of the servo valve. All of which will seriously deteriorate the barrel pitching system’s control performance. For this purpose, a new cascade control method based on active disturbance rejection control (ADRC) and proportional integral derivative (PID) for the vehicle mounted and unbalanced BPS is proposed. In this paper, the working mechanism is analyzed and the mathematical model of the BPS is established. Moreover, the sensitivity equation of BR and EW about the BPS is constructed and their influence are respectively dissected, then the evolution model and law of core parameters under the condition of BR and EW are deduced and researched. In the process of controller design, the correction element and isolation element are, respectively, used for compensating and suppressing the influence of EW and BR, then the ADRC and PID are synthesized to obtained the cascade control for the BPS. Finally, the effectiveness of the proposed method is verified through simulation experiments.

     

A nondestructive mechanoelectrical method for determining the strength of concrete under variable temperature and humidity conditions

An algorithm for the mechanoelectrical nondestructive method for determining the mechanical strength of concrete is developed. The proposed method based on the phenomenon of mechanoelectrical transformations has a higher accuracy of determining the mechanical strength than the accuracy inherent to the sclerometry method, which is applied in practice, and can be used in tests of materials under different temperature and humidity conditions.