Methods for estimating the durability of the needle bearing of the piston head of the connecting rod of a transportation diesel

The article presents the results of an experimental study and analytical evaluation calculations to check service life and increase durability of the needle bearing of piston head of connecting rod of a transport diesel engine. The primary reasons for the violation of the nominal operation of the main units of this mechanism have been established. Corresponding recommendations are proposed for carrying out accelerated tests for durability, reducing the thermal loads of the bearing operation and, as a consequence, improving the quality and service life of its entire piston group. Theoretical and experimental methods for determining the nominal life of the needle bearing of the piston head of the connecting rod (PHCR) of a transport diesel engine are proposed. The theoretical methodology allows obtaining reliable values of durability, taking into account the distribution of the working load over the rolling elements, as well as the mobility of the piston pin and sleeve. The performed calculations make it possible to correct and clarify the standard mathematical model for determining the nominal life of the PHCR needle bearing, depending on the distribution of loads on the rolling elements (rollers) under different operating conditions. This experimental technique with an acceleration factor of 10 is based on a twofold increase in the force effect on the elements of the PHCR needle bearing. This was achieved by assembling the bearing using a special technology, which is described in detail in the work. A significant decrease in the thermal effect and a decrease in radial loads on working rollers have been established. For ensure the regular oil supply into bearing during engine operation, a technique was developed to increase the load on the roller in contact zone, which significantly influenced durability and made it possible to conduct accelerated tests with a reliable yield. Its results of operational research and experience in design work correlate and are sufficiently explained by the developed methods, which allows them to be used for the improvement and modernization of connecting rods with needle bearings in PHCR. That is a permission to use these methodic for doing perfect and modern the needle bearing of the connecting-rod piston. Keywords: diesel, test procedure, needle bearing, rollers, piston head of the connecting rod, durability.

Reliability degradation prediction of photovoltaic modules based on dependability methods

PurposeThe reliability prediction is among the most important objectives for achieving overall system performance, and this prediction carried out by anticipating system performance degradation. In this context, the purpose of this research paper is to development of methodology for the photovoltaic (PV) modules' reliability prediction taking into account their future operating context.Design/methodology/approachThe proposed methodology is framed by dependability methods, in this regard, two methods of dysfunctional analysis were used, the Failure Mode and Effects Criticality Analysis (FMECA) method is carried out for identification of the degradation modes, and the Fault Tree Analysis (FTA) method is used for identification the causes of PV modules degradation and the parameters influencing its degradation. Then, based on these parameters, accelerated tests have been used to predict the reliability of PV modules.FindingsThe application of the proposed methodology on PWX 500 PV modules' in different regions of Algeria makes it possible to predict its reliability, taking into account the future constraints on its operation. In this case, the temperature and relative humidity vary from one region to another was chosen as constraints. The results obtained from the different regions confirms the reliability provided by the designer of the Saharan cities Biskra, In Salah, Tamanraset, and affirms this value for the two Mediterranean cities of Oran and Algiers.Originality/valueThe proposed methodology is developed for the reliability prediction of the PV modules taking into account their future operating context and, the choice of different regions confirms or disproves the reliability provided by the designer of the PV modules studied. This application confirms their performance within the framework of the reliability prediction.

Comparison between Accelerated Tests and Natural Exposures for Organic Coating Protective Systems Based on EIS Parameters

The equivalent relationship between accelerated tests and natural exposures has been extensively studied over the past several years to estimate the service life of a barrier organic coating protective system. Herein, based on the probability density function (PDF) theory, a mathematical expression that describes the limit value of the low-frequency impedance (RL) of a barrier organic coating protective system as a function of the elapsed time is proposed in form of Arrhenius formula under certain assumptions, and the degradation coefficient is defined. This expression was consistent with the results of the accelerated tests. The equivalent relationship between accelerated tests and natural exposures, established based on the equivalence principle, was utilized to predict the service life of the coated Al alloy in an ocean atmospheric environment.

METHODOLOGICAL APPROACHES TO ACCELERATED TESTS OF CRUSHING KNIVES OF GRINDING CATS. COMPARATIVE TESTS OF LOSS OF CUTTING CAPACITY

The purpose of the research is to analyze the design features and parameters of grinding knives to compare the intensity of loss of cutting ability of each of the models of knives depending on the load cycles. Methods and materials. Conduct an analytical inspection and instrumental studies of the blades of grinding rollers type KR with different design features. Carry out bench accelerated tests based on the cyclic impact load of the knife fragment due to falling on the simulator of wear cycles and check the residual cutting capacity on the cutting simulator. Justify the coefficient of acceleration of tests as a derivative of hardness and density of the simulator, as well as the ratio of the energy of the fall of the knife fragment on the stand and its rotational motion in the field. Statistical analysis of experimental data was performed by analysis of variance and interpreted by standard computer programs Excel in the form of graphs. Results. Analyzing the proposed method for determining the intensity of loss of cutting ability of the knife when it falls on the simulator of plant debris allowed to rank different models and establish their relative resource. Unhardened models of both 45 and 30MnB5 Steel provide low life and their residual cutting ability is only 15-25% compared to hardened models. Analyzing the research results, the hardened model of a knife made of 45 Steel withstands 4 times more load cycles compared to unhardened models, but is inferior to the hardened model of Steel 30MnB5 (borista), which has the highest resource. Even after 150 load cycles (in terms of the work of a roller with a width of 12.5 m - operating time of more than 1000 ha), it retains more than 55% of the initial cutting ability, which is characterized by low intensity of its loss. Conclusions. According to the tests of the intensity of loss of cutting ability of knives, the most acceptable option for the equipment of roller-shredders is a hardened model made of 30MnB5 Steel (borista), which has the highest resource.

The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates

The effectiveness of accelerated tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates was evaluated. The Accelerated Mortar Bar Test was found effective for evaluating potential alkali-reactivity when the test variables, such as crushing method and absorption, are carried out in a well-defined process. The method of crushing was found to have significant impact on the expansion. The Concrete Microbar Test (CMBT) provides good correlation to the expansion of Concrete Prisms incorporating Supplementary Cementing Materials when an expansion limit of 0.10% at 56 days or 0.04% at 28 days were used, based on the limited number of tests carried out here.

The Efficacy of Accelerated Test Methods to Evaluate Alkali Silica Reactivity of Recycled Concrete Aggregates

The effectiveness of accelerated tests in evaluating the Alkali-Silica Reactivity of Recycled Concrete Aggregates was evaluated. The Accelerated Mortar Bar Test was found effective for evaluating potential alkali-reactivity when the test variables, such as crushing method and absorption, are carried out in a well-defined process. The method of crushing was found to have significant impact on the expansion. The Concrete Microbar Test (CMBT) provides good correlation to the expansion of Concrete Prisms incorporating Supplementary Cementing Materials when an expansion limit of 0.10% at 56 days or 0.04% at 28 days were used, based on the limited number of tests carried out here.

Influence of Carbonization of Concrete Surfaces on their Adhesion with Freshly-Laid Concrete

During operation, concrete and reinforced concrete structures are exposed to the aggressive environment of carbon dioxide. During the reconstruction and overhaul of the berthing facilities in the coastal zone of the seas of the Far East, a weak bond strength of the “old” carbonated and “new” repair concrete has been established in the paper. The reason that prevents reliable adhesion of concrete is the formation of fragile corrosion products in the pores and on the surface of “old” concrete. Accelerated tests of concrete carbonization from exposure to carbon dioxide have been carried out in the course of the study. The structure of the carbonized cement stone has been examined using a scanning electron microscope. The research results have made it possible to assess the structure of a “healthy” cement stone and affected by carbonization. The performed analysis of concrete carbonization process, including micrographs of the samples, has shown that under the action of carbon dioxide, the surface layer with a thickness of 4 mm and more undergoes structural restructuring. Fibrous formations are destroyed, and the carbonized volume is a heap of loosely bound loose new formations and films blocking the entrances to the capillary system of concrete. They are not a reliable basis for adhesion of “new” and “old” concrete and prevent the penetration of liquid containing cement dissolution products from “new” concrete into the capillaries of the healthy structure of the “old” concrete for their reliable connection.