ABRAZIVE FLUID – MEANS OF IMPROVEMENT THE GEOMETRIC CHARACTERISICS OF THE DIESEL NOZZLE EXHAUST MICROCHANNEL

In order to obtain automobiles that comply with the increasingly severe pollution standards, as well as to obtain some of them at low costs, a technical-economic approach to the flow of the fuel fluid through the flow holes of the injection nozzles is necessary. Through the effect of hydropolishing the geometric characteristics of the hydraulic flow path, the flow path is modeled, reducing cavitation and achieving high performance. The fluid used is a fluid that has properties close to diesel and has SiC microparticles in suspension (manufacturing costs in in this case they are reduced). The article contains an analysis of the influence of the abrasive flow on the geometric parameters of the nozzle and implicitly on the operation of thermal engines. The results provide a means of identifying parameters that can be compared and evaluated in order to achieve the desired level of hydrodynamic efficiency

Reliability Estimation of Towed Grader Attachment Using Finite Element Analysis and Point Estimation

The paper presents an analysis of the reliability of front blade, rear blade and frame of the towed grader as well as experimental validation of the results obtained from the finite element analysis. The analyzed prototype was designed for maintenance and repair of forest roads and equipped with two types of blades for cleaning and levelling the ground surface. Lifetimes of towed grader attachments can be estimated with high accuracy using three-parameter Weibull distribution. The values of the location parameter γ were determined by using the maximum values of the correlation coefficient, while the method of maximum likelihood was used for the point estimation of the parameters. Because higher values of the shape parameter had been obtained, the point estimation and estimation with confidence intervals of components lifetimes were performed. The analysis of the results indicates that the used assumptions may not fully take the complex stresses encountered in use into account

Modern Technologies for Micro-drilling of the Fuel Injector Nozzle used in Motor Vehicles - A Review of the Literature

To cope with the pollution norms and an improvement of the combustion of the internal combustion engines, high-quality holes with diameters smaller than 145 µm are needed for the manufacture of fuel injection nozzles. The current practice of using drilling by electro-discharge machining of fuel injection nozzles is limited in terms of the size of the hole it can efficiently produce and the time required for drilling. In addition, the cost of the tool is high. This paper presents an investigation into a sequential laser and electro-discharge micro-drilling technique for the manufacture of fuel injection nozzles. A pilot hole drilled with a laser is removed by electrodischarge. It was found that this hybrid process eliminated the problems of reformed and heat-affected areas usually associated with the laser drilling process. The new process has allowed a reduction in total drilling time compared to standard electro-discharge machining drilling, as less material is removed from the electro-discharge machining. The quality of the holes is as good as direct electro-discharge machining drilling. This technique has allowed valuable cost savings and increased production capacity for the manufacture of the fuel injector nozzle

Statistical inferences for bearings life using sudden death test

In this paper we propose a calculus method for reliability indicators estimation and a complete statistical inferences for three parameters Weibull distribution of bearings life. Using experimental values regarding the durability of bearings tested on stands by the sudden death tests involves a series of particularities of the estimation using maximum likelihood method and statistical inference accomplishment. The paper detailing these features and also provides an example calculation

OPTIMUM DESIGN OF EXPERIMENTS FOR ACCELERATED RELIABILITY TESTING

In this paper is presented a case study that demonstrates how design to experiments (DOE) information can be used to design better accelerated reliability tests. In the case study described in this paper, will be done a comparison and optimization between main accelerated reliability test plans (3 Level Best Standard Plan, 3 Level Best Compromise Plan, 3 Level Best Equal Expected Number Failing Plan, 3 Level 4:2:1 Allocation Plan). Before starting an accelerated reliability test, it is advisable to have a plan that helps in accurately estimating reliability at operating conditions while minimizing test time and costs. A test plan should be used to decide on the appropriate stress levels that should be used (for each stress type) and the amount of the test units that need to be allocated to the different stress levels (for each combination of the different stress types' levels). For the case study it used ALTA 7 software what provides a complete analysis for data from accelerated reliability test

Reliability analysis of scarifying tooth for trailed scarifier

In this paper are estimated the reliability indicators of scarifying tooth for trailed scarifier. Taking into account the constructive and technological factors, as well as the duration of exploitation, the determined values of Anderson-Darling statistics indicates that the Weibull distribution permits to model with maximum accuracy the lifetime of such attachment. The location parameter is estimated using the correlation coefficient method and minimum lifetimes are determined experimentally. Analyzing the obtained parameters, it can be shown that it can be used the normal distribution for reliability estimation. In this respects, it was applied the point and confidence interval estimation of the average and standard deviation lifetime of scarifying teeth of trailed scarifier

Reliability analysis of scarifying tooth for trailed scarifier

In this paper are estimated the reliability indicators of scarifying tooth for trailed scarifier. Taking into account the constructive and technological factors, as well as the duration of exploitation, the determined values of Anderson-Darling statistics indicates that the Weibull distribution permits to model with maximum accuracy the lifetime of such attachment. The location parameter is estimated using the correlation coefficient method and minimum lifetimes are determined experimentally. Analyzing the obtained parameters, it can be shown that it can be used the normal distribution for reliability estimation. In this respects, it was applied the point and confidence interval estimation of the average and standard deviation lifetime of scarifying teeth of trailed scarifier

Reliability analysis of scarifying tooth for trailed scarifier

In this paper are estimated the reliability indicators of scarifying tooth for trailed scarifier. Taking into account the constructive and technological factors, as well as the duration of exploitation, the determined values of Anderson-Darling statistics indicates that the Weibull distribution permits to model with maximum accuracy the lifetime of such attachment. The location parameter is estimated using the correlation coefficient method and minimum lifetimes are determined experimentally. Analyzing the obtained parameters, it can be shown that it can be used the normal distribution for reliability estimation. In this respects, it was applied the point and confidence interval estimation of the average and standard deviation lifetime of scarifying teeth of trailed scarifier

Experimental Study of Static and Fatigue Behavior of CFRP-Balsa Sandwiches under Three-point Flexural Loading

Balsa wood is a natural cellular material with an excellent resistance-to-weight ratio that is ideal for manufacturing the core of sandwich structures. In this study, sandwich specimens with a carbon-fiber-reinforced polymer (CFRP) skin and a balsa wood core were tested with static and dynamic loading. Three-point flexural tests in static regime determined the mechanical characteristics of the CFRP-balsa specimens that were needed for subsequent fatigue strength tests. Also, experimental research was performed on the Charpy impact response of the CFRP-balsa sandwich specimens. This study implemented an accelerated fatigue testing method to identify and predict the mean fatigue life of the CFRP-balsa sandwich specimens subjected to cyclic fatigue via three-point flexural tests. Using the accelerated fatigue and the three-point flexural testing methodology on the CFRP-balsa sandwich specimens, the testing period was reduced by 11.9 times, and thus the material costs necessary for the tests were also reduced. Also, the breaking surfaces were analysed to reveal the failure modes of CFRP-balsa specimens subjected to static and fatigue tests at three-point flexural and at impact tests