The author has something to say
For a long time, our products can meet the requirements of performance and function in the laboratory test, but once delivered to the user after a certain period of time, there will be this or that problem, the author has been deeply confused about this, and also deeply felt that it is necessary to incorporate the environmental adaptability assessment of the product into the process of product testing and testing, and solidify this into a test program, the environmental assessment of the product research to in-depth.
INTRODUCTION
Modern equipment is not only faced with vehicle-mounted, ship-based, airborne, indoor, field, border and coastal defense conditions, but also climatic environment, mechanical environment, electromagnetic environment, biological and chemical environment, etc., in addition to meeting the basic tactical indicators of the product, whether it can adapt to the complex and changeable environment has also become an important feature of the equipment. The General Requirements for Equipment Environmental Engineering (GJB 4239) clearly stipulates that environmental adaptability is the ability of equipment to achieve all its predetermined functions, performance and/or not be damaged under the action of various environments that may be encountered during its life expectation, and is one of the important quality characteristics of equipment.
Therefore, continuously improving the environmental adaptability of military equipment is a topic that equipment manufacturing plants and their structural and process designers always need to pay attention to and strengthen research, and it is also an important factor in whether equipment can form combat effectiveness.
1 The need for environmental adaptation studies
In recent years, our institute has produced a number of sets and varieties of liquid cooling source equipment for troops and institutes, and the products cover a variety of environmental conditions such as small liquid cooling sources for laboratories, air-conditioned vehicles that provide a guarantee environment for the engine room, radome environmental control air conditioners, large-scale liquid cooling sources that provide cold sources for lasers, and special dehumidification and constant temperature equipment. With the continuous delivery and use of liquid cooling source equipment, several problems and defects of products appear accordingly, which are mainly manifested in outstanding problems such as insufficient environmental adaptability design of products, insufficient environmental tests before product delivery, and lack of environmental test evaluation methods.
In view of the above shortcomings, we take GJB 4239 as the guiding principle and the environmental adaptability design of the product as the breakthrough point, and initially form and improve a set of environmental adaptability design and test verification specifications, which has been proved in practice to obtain good results and gradually improve customer satisfaction.
2. Liquid cooling source environmental adaptability design
2.1 Design Principles
The liquid cooling source works by means of phase change refrigeration, continuously brings out the heat in the load through the water pump, and can provide constant flow, pressure, and temperature cooling medium for the hot end of the load, so as to ensure the stable and reliable work of the load, of which the compressor, water pump, radiator and controller are its main components, according to the tasks and roles they undertake, they can be roughly divided into mechanical refrigeration units, coolant circulation units, various types of regulation (flow, pressure regulation) units, and electronic control units. It can be seen that the liquid cooling source is a set of more complex electromechanical equipment, and each unit interacts and influences each other in operation, so in the environmental adaptability design, the various environmental factors and stresses that the liquid cooling source may experience in the actual use scenario should be fully considered, starting from the operation characteristics of each electromechanical unit, heat flow pipeline, electronic controller, etc. in the liquid cooling source, according to the system, the whole machine, the unit, the parts, the module, The sequence of components to materials is clarified step by step, and structural design, material optimization, process measures, redundancy design and other methods are adopted in a targeted manner, so as to achieve the expected environmental adaptability design requirements.
2.2. Establish a library of environmental loads and their typical failure modes
Through the analysis of environmental load requirements, consulting relevant information and the accumulation of many years of product design and maintenance experience, we have established a failure mode library of typical failure modes generated by environmental loads to provide reference for designers, as shown in the following table:
Table 1 Environmental loads, major impacts, and typical failure modes2.3 Main measures taken
2.3.1. Structural design
a) The compressor exhaust pipe is designed with a damping pipe and a muffler. The stiffness of the connecting pipe should be reduced for the pipeline connected to the compressor, and the disturbance and flexibility of the pipeline should be appropriately increased without affecting the performance, so as to reduce the binding effect of the pipeline on the compressor, ensure the safety of the piping pipeline, reduce the vibration of the piping pipeline, and prevent it from producing resonant sound. The compressor body should be made of shock-absorbing materials or shock-absorbing structural parts with good vibration damping performance according to the actual use scenarios (such as vehicle-mounted, ship-based, airborne, etc.), so as to achieve the purpose of reducing the vibration of the compressor and preventing its transmission.
b) When the coolant pipe is laid, the pipe support, elevator, and wall should also be dampened. The usual methods are: pipe and support, elevator between the cushion soft material, the use of vibration isolation hanger (spring, rubber). Regardless of whether the fluorine system piping or the water system piping must take effective vibration reduction measures. The pump is connected to the water pipe with a flexible hose so that the vibration of the equipment is not transmitted to the pipeline. In this system, it is recommended to use stainless steel metal hose connections for the connection between cabins.
c) Vibration damping design of the controller.
The cabinet where the control unit is located is made of 1 2 mm thick stainless steel plate bending and welding, and the bottom plate is made of 2 mm thick stainless steel plate bending and welding, because there are more electronic components installed inside, the electric control cabinet is welded with horizontal braces and vertical braces inside to enhance the overall rigidity of the electric control cabinet; Improve the structural stiffness, protect against low-frequency excitation, and the low-frequency vibration protection measures of the component structure are shown in the following table.
Table 2 Low-frequency vibration protection measures for components2.3.2. High and low, temperature and thermal shock resistant design
The cooling system frame, pipeline and other structural parts are made of stainless steel or rust-proof aluminum plate and other materials, and low-temperature resistant water pumps, fans, valves, cables and other components and seals are selected, and the electrical components should meet the requirements of working temperature and storage temperature, and the components should be screened for stress such as high and low temperature and random vibration before storage; The outer surface is sprayed with paint that can withstand high and low temperatures.
2.3.3 Rainproof design
The heat dissipation unit is designed with rainproof louvers and movable dampers, the surface of the equipment is designed with optimized structure to reduce rainwater sedimentation, and reasonable material selection is carried out, and the exposed metal parts and electrical equipment are protected to improve the protection level.
Table 3 Rain test conditions according to the above conditions, after the test should not produce water leakage, water seepage, etc., the insulation and leakage detection should be carried out at the same time, which should meet the requirements of the relevant judgment criteria.
2.3.4 Three-proof design
1) Material optimization: While meeting the structural requirements, reasonable material selection is one of the important means to prevent and mitigate product corrosion, deterioration and deterioration. While selecting materials that can resist harmful environmental factors, it should also meet electrical, mechanical, physical, processing performance, cost and other requirements;
2) Process protection: Process protection is an effective measure to meet and improve the environmental adaptability of environmental control equipment. The use of heat treatment, processing technology and reasonable assembly process can eliminate stress and deformation; The corrosion resistance of the material can be improved through surface passivation, anodizing, Teflon plating and other methods;
3) The main protection design and process measures of liquid cooling source.
The frame and structural parts are made of stainless steel 304 material, and the surface is plated;
The pipes, joints and water tank are made of stainless steel 316L material, and the heating components are treated with Teflon to prevent corrosion and scaling;
Pipeline solder joints are pickled and passivated;
The radiator adopts copper tube and copper fins;
The copper pipe is welded with high silver, and the surface is cleaned and dried after welding, and the surface is coated with clear oil after welding.
3. Verification and evaluation of environmental adaptability test
Fig.1 In the design stage, the main environmental adaptability test was carried out to analyze the environmental profile of the product life cycle in combination with user requirements and usage scenarios, including laboratory environment and natural environment, and the main environmental impact factors were obtained. Combined with the relevant test standards of GJB150A, we have formulated scientific test items (outlined as follows):
Table 4 After a series of environmental adaptability tests for a typical environmental test project, the R&D department prepares an environmental test design compliance analysis report, summarizes and reviews the environmental test of the prototype, and puts forward improvement suggestions and avoidance measures in a timely manner according to the mechanism of environmental impact factors and the key points that affect or weaken environmental adaptability, so as to provide an important evaluation and design basis for the environmental adaptability design in the design finalization stage.
4 Concluding remarks
Environmental adaptability requirements are one of the important quality characteristics of equipment. In this paper, by combining the characteristics of product structure, task characteristics and life environment profile, a variety of environmental impact factors and data are collected, and an environmental load failure mode database and environmental database are established to form a relatively reasonable and perfect environmental test verification system. In addition, the design and quality department combines the relevant requirements of G J B 4239-2001 on environmental engineering management to carry out design requirements, analysis reports, reviews and evaluations, so as to implement the environmental adaptability design.