Optimal design of a novel crash box with functional gradient negative Poisson’s ratio structure

Crashworthiness and anti-vibration performance play critical roles in the performance of passenger cars. Aiming at enhancing the crash resistance and vibration resistance of vehicles thus providing good protection for passengers and drivers, a novel crash box with three-dimensional double arrow type negative Poisson’s ratio structure with functional gradient filling inner core (FGNPR crash box) is introduced in this paper and its performance is studied in detail through the comparison with the conventional crash box and the crash box filled with the uniform gradient negative Poisson’s ratio structure (NPR crash box) in crashworthiness and vibration resistance. Furthermore, range analysis is used to screen out the design variables that have little influence on the evaluation indexes and eliminate them. Based on these, neighborhood cultivation genetic algorithm (NCGA) and non-dominated sorting genetic algorithm-ii (NSGA-II) are selected as the optimization algorithms to carry out optimization design respectively and a comparison is made between the two suboptimal results screened out based on the normal boundary intersection (NBI) method to determine the overall optimal solution. Results show that the optimized FGNPR crash box has better crashworthiness and vibration resistance over the other crash boxes and its performance is further verified based on the peak acceleration of B-pillar in full vehicle crash condition. This paper provides some theoretical reference support for the development and exploration of automobile crash box systems.

Development of a Method for Obtaining a Wear-Resistant Coating for a Cutting Tool

The article presents a method for producing a nanostructured wear-resistant high-hard coating with high physicomechanical and strength characteristics, resistance to shock and vibration loads. The result is an increase in adhesion between the substrate and the coating, as well as an increase in microhardness. One of the common methods of metal cutting is band-cutting machines that use closed band saws as cutting tools. Since materials with high physicomechanical characteristics (hardness, strength, etc.) are increasingly being used in modern production, which significantly complicates the cutting process and makes increased demands on the cutting tool. To expand the range of processed materials for which the productive use of band-cutting machines is possible, it became necessary to create a band saw with higher cutting characteristics. At the same time, the specificity of the working conditions of the band saw shows that the blade should have such characteristics as increased vibration resistance, resistance to alternating and dynamic loads, and the cutting part of the saw should have increased resistance to shock, dynamic, alternating loads, have high hardness, as well as increased wear resistance.

Analysis of vibration resistance of machining technological equipment of a floating workshop in shipbuilding

В статье рассмотрены результаты исследований в направлении совершенствования станочного оборудования для высокоточной обработки деталей в условиях плавучих мастерских путем повышения виброустойчивости технологической системы и снижения вредных воздействий от внешней среды (морского волнения) и соседнего работающего оборудования. Проанализированы традиционные виброизолирующие опоры современных станков, которые невозможно использовать на плавучих мастерских по причине потери ими функционирования в условиях качки плавучего основания и горизонтальных смещений под ее воздействием. Разные способы установки обеспечивают различную степень чувствительности станка к колебаниям основания и возмущениям, действующим в станке. Целью работы является изыскание путей повышения эффективности систем виброизоляции станочного оборудования в условиях плавучей мастерской для обеспечения качества обрабатываемых деталей. Задачей является анализ традиционных виброизолирующих устройств и разработка модели и алгоритма поиска новых структурных вариантов виброизолирующих устройств для уменьшения влияния вибрационных воздействий от внешней среды и внутренних факторов на качество обработки. Выявлено, что на этапах анализа и синтеза на уровне структурно-компоновочной оптимизации виброизолирующих устройств возможно по укрупненным качественным показателям получение рациональных структурных вариантов для шлифовальных станков плавучей мастерской. Установлено, что путем параметрического синтеза и проведения дополнительных теоретических и практических исследований реальных конструкций виброизолирующих устройств, возможно создание новых конструкций виброизолирующего устройства механообрабатывающего технологического оборудования. The article discusses the results of research in the direction of improving machine tool equipment for high-precision machining of parts in floating workshops by increasing the vibration resistance of the technological system and reducing the harmful effects of the environment (sea waves) and neighboring operating equipment. The traditional vibration-isolating supports of modern machines, which cannot be used in floating workshops, due to their loss of functioning under the conditions of the floating base swinging and horizontal displacements under its influence, are analyzed. Different installation methods provide different degrees of machine sensitivity to base vibrations and disturbances in the machine. The aim of the work is to find ways to improve the efficiency of vibration isolation systems for machine tool equipment in a floating workshop to ensure the quality of processed parts. The task is to analyze traditional vibration damping devices and develop a model and an algorithm for searching for new structural variants of vibration damping devices to reduce the influence of vibration effects from the external environment and internal factors on the quality of processing. It was revealed that at the stages of analysis and synthesis at the level of structural and layout optimization of vibration isolation devices, it is possible to obtain rational structural options for grinding machines of a floating workshop based on enlarged quality indicators. It has been established that by means of parametric synthesis and additional theoretical and practical research of real designs of vibration-isolating devices, it is possible to create new designs of vibration-isolating devices of mechanical processing equipment.

Identifying Delay Time of Detonator for a Millisecond Blasting

Based on wavelet transform, the blasting vibration signals are analyzed here. For millisecond blasting, the blasting effect is mostly affected by the actual delay time. Local characteristics of the analyzed signals could be highlighted by the wavelet transform. The simultaneous initiation of large explosive quantity could be avoided by the use of multistage detonators, while the vibration resistance effect could be better. For the same level of detonator segment, the larger the arranged time interval, the less the possibility of initiation at the same time, which is not conducive to the vibration resistance. Therefore, it is suggested to use high-level detonators with detonating cord or high-precision digital electronic detonators to minimize the initiation error. Furthermore, by identifying the delay time using wavelet transform, the interval delay time of different detonator segments could be obtained. Moreover, the nominal delay time, actual delay time, and interval delay time are further compared and analyzed. It is suggested that the millisecond delay series of detonators should be selected in the whole section blasting, and the segment should be jumped as much as possible, so as to increase the secondary breakage time. Detonators with longer interval delay time should be avoided to the full.

Identification of the Model of the Dynamic System of a Milling Machine Based on the Study of Vibroacoustic Characteristics

In this paper, the authors propose a method for ensuring the reliability of the computational model intended for the study of dynamic processes in technological cutting systems. The advantage of using 3D models in CAD/CAM/CAE systems for solving such problems is shown. The method of conducting an experimental study to identify the calculated model by natural frequencies is justified. The method is proposed for adjusting the 3D model in order to ensure that the dynamic pattern occurring during cutting corresponds to experimental processes. The authors give a concrete example of solving the problem of identifying the computational model of the dynamic system of a milling machine. An example of solving the applied problem of optimizing cutting modes in terms of vibration resistance parameters using the identified computational model is also given.

Ensuring energy efficiency of transmissions of cars and tractors during modernization with a change in the number of cylinders of the internal combustion engine

The article investigates the energy efficiency of motor-transmission units when using internal combustion engines with different numbers of cylinders. Transmissions, those in a unit with piston internal combustion engines are loaded with uneven torque, which is the cause of torsional vibrations of their parts. Torsional vibrations create additional dynamic loads on the transmission elements, and also reduce its efficiency. To ensure a high level of energy efficiency of the engine-transmission unit, the elastic-inertial parameters of the transmission must be matched with the amplitude-frequency characteristics of the torque of the installed engine. When replacing a serial internal combustion engines with an engine with output characteristics different from the prototype, it is necessary to assess the vibration resistance of the modernized engine-transmission unit, which was done in this work. As a criterion for vibration resistance of the modernized machine unit, the cyclic elastic efficiency of the transmission was used. This factor takes into account the natural frequency of the transmission input shaft, as well as the amplitude and frequency of vibration of the engine torque. The decisive influence on the vibration characteristics of the engine is exerted by the rotational speed of its crankshaft and the number of cylinders. When conducting a comparative assessment of the energy efficiency level of the modernized engine-transmission unit, it was assumed that before the modernization the transmission was in a unit with a single-cylinder internal combustion engine. As a result of the study, the conditions for ensuring the vibration resistance of engine transmission units have been determined, a method has been developed for comparative analysis of the energy efficiency indicators of engine transmission units with different numbers of internal combustion engine cylinders, and possible ways to increase the energy efficiency of engine units of cars and tractors during modernization with a change in the number of internal combustion engine cylinders are indicated.