Stiffness Evaluation and fast matching method of mechanical composite structure

Stiffness evaluation can improve the reliability and safety of combined machinery, which is often used to evaluate the performance of combined machinery. In order to study the stiffness evaluation method and rapid matching of mechanical composite structure, the composite machinery composed of high-power diesel is taken as the research object. The results show that the error between test mode and calculation mode is no more than 10%, indicating the reliability of finite element simulation model; two characterization methods of static stiffness and dynamic stiffness are determined, and the analysis methods of two characterization methods of combined machinery are discussed one by one. Taking the combined machinery of body, main bearing cap and oil pan as the research object, the overall stiffness characterization data of three parts are obtained one by one; finally, the principles of mechanical combination Stiffness Evaluation and rapid matching are summarized. This study provides a reference for Stiffness Evaluation and rapid matching of combined mechanical structures.

“Double Evaluation”-the prerequisite and foundation of the municipal-level land and space master plan

Resources and environment carrying capacity and space development land suitability assessment (after referred to as “double evaluation”) is to recognize the location of natural resources and land space development short board, Highlight the important prerequisites and foundations for the governance and problem orientation of land and space planning in the new era, Played an important role in co-ordinate the three types of layout space to find out the natural resources[1-3], to identify the type of risk, determine the bearing cap and scientific delineation of three control lines, At the same time, it also provides an important starting point for the implementation of monitoring, evaluation and early warning of land and space planning. In order to better support the preparation of land and space planning in the new era, it is necessary to re-examine and re-understand the “double evaluation” work of municipal land and space planning. This article starts with the “Guidelines for the Compilation of Municipal-level Territorial and Spatial Master Plan (Trial)” (hereinafter referred to as “Guide”) for the work requirements of “double evaluation”, through combing and summarizing the existing problems and important difficulties in actual work, from logical transformation and technical mining The “double evaluation” work is summarized and explored from a dual perspective, in order to provide a reference for the preparation of the municipal-level land and space master plan.

The effects of material and structure of main bearing caps on crankshaft lubrication of diesel engine

The elastic deformation of the crankshaft and engine block has important effects on lubrication performance of main bearings of the diesel engine. But the effect of main bearing caps was rarely analyzed. The purpose of this article is to analyze and compare the tribological performances of main bearings of a 20-V medium-speed diesel engine with different materials and structures of main bearing caps. A coupled multi-elastic body and elasto-hydrodynamic model is established for a 20-V medium-speed diesel engine. The deformations of engine block, crankshaft and bearing caps are simulated with finite element modal condensation method. The bearing lubrication analysis is based on the extended Reynolds equation considering the deformation of contact surface and solved by finite difference method. Two materials and four structures of the main bearing cap are analyzed with the coupled model. The distribution of oil film pressure, thickness and bearing thermal loads are obtained and analyzed. The main bearing cap of iron is better than steel on bearing lubrication performance. With the lower edge stiffness of bearing cap, the maximum oil film pressure of bearing can be reduced by 13%. Meanwhile, the bearing thermal load can be reduced by 53%. The results show that when the bearing cap material is iron and with large trough on both sides of bearing cap, the peak value of edge pressure and the average heat load of main bearing can be reduced effectively under the premise of ensuring stiffness.

The Evolution and Sources of Major Ions in Hot Springs in the Triassic Carbonates of Chongqing, China

Thermal groundwater in the Lower and Middle Triassic carbonates in Chongqing, China, is mainly concentrated in anticlines. Hot springs (32.9 to 57 °C) with SO4-Ca type waters and Total Dissolved Solids (TDS) of 1620 to 2929 mg/L emerge in the middle and the plunging ends of the structures. Multivariate methods are used to analyze the hydrochemical characteristics of the waters, and identify the sources of the main dissolved components, providing an insight into the evolution of the environment in which they formed. Hierarchical cluster analysis of compositional data differentiates samples in the study area into three categories: high TDS-high Ca2+ and SO42− water; medium TDS-high Na+ and Cl− water; and low TDS-high HCO3− water. Factor analysis and ion ratio relationships show that Ca2+ and SO42− are mainly derived from the dissolution of gypsum and anhydrite within the geothermal reservoir, with some addition of SO42− from coal-bearing cap rocks. The main source of HCO3−, is in the dissolution of dolomite and CO2 that also promotes the incongruent dissolution of albite and K-feldspar, adding Na+ and K+ to the groundwater. Reverse modelling of the transfers of each phase shows, in three models, that the minerals dissolved decrease progressively—with the exception of halite and albite. Combined with the hydrochemical characteristics of hot water in the same reservoir in the adjacent area (Cl-Na type, TDS of 13.37 g/L), a process of desalination of the hot water can be confirmed, which has not yet reached the ‘freshwater’ stage dominated by HCO3−.

Die Design for Main Bearing Cap of Engine Block Based Semi-Solid Die Casting Process and the Comparison Analysis with Squeeze Casting Process

There are two new processes to development automobile structural components which have certain thickness. In the present paper, taking a main bearing cap product as an example, analyses die design by comparing the experimental and computational numerical simulation results. For the main bearing cap, product structure and mold design were designed to be suitable for characters of SSM die casting and squeeze process. Semi-solid slurry has significantly higher viscosity than liquid metal. This character of fluidity and solid fraction phase make the flow condition more laminar than liquid squeeze casting with the partial fill experiment. And compared with squeeze casting process, the globular shape grain size is smaller than dendritic structure. And mechanical property result shows that the elongation of SSM die casting can achieve more than twice than squeeze casting.

Reduced-Order Modeling of Preloaded Bolted Structures in Multibody Systems by the Use of Trial Vector Derivatives

In order to achieve a correct representation of jointed structures within multibody dynamic simulations, an accurate computation of the nonlinear contact and friction forces between the contact surfaces is required. In recent history, trial vectors based on trial vector derivatives, the so-called joint modes, have been presented, which allow an accurate and efficient representation of this joint contact. In this paper, a systematic adaption of this method for preloaded bolted joints is presented. The new strategy leads to a lower number of additional joint modes required for accurate results and hence to lower computational time. Further, a major reduction of the computational effort for joint modes can be achieved. The potential and also possible limitations of the method are investigated using two numerical examples of a preloaded friction bar and a bolted piston rod bearing cap.

Experimental and Numerical Study on the Fretting Fatigue Mechanism of the V Type Engine

Fretting fatigue is one of the typical failure forms of engine block. The aim of this study is to investigate the fretting fatigue mechanism of the V type engine and guide engine design. An experiential system was developed to simulate fretting fatigue failure under typical engine working condition. And a submodel was used in the finite element calculation to analyze contact status and stress distribution of the structural model. Through the fretting fatigue experimental observations and finite element analysis, it can be concluded that the additional rotate torque caused by bearing load and the bolt pretension load are the two main factors which affect the fretting fatigue mechanism of the V type engine. Appropriate increasing of the bolt pretension load and using extended skirt block with cross-bolted main bearings design will restrain the oscillation of the main bearing cap can be beneficial to fretting fatigue lives of the engine block.