1. Definitions
3. The comprehensive test chamber is a high-end test equipment that can simulate three environmental stresses: temperature, humidity and vibration simultaneously or alternately. It integrates the climate environment simulation system with the mechanical environment simulation system to realize the combined condition control of temperature, humidity and vibration in the working space of the test chamber, so as to build a comprehensive environmental field close to the real one. This equipment can apply temperature cycle changes, humidity penetration and vibration excitation of specified spectrum and magnitude according to preset procedures in the same test chamber, so that the test product can withstand the synergistic effect of multiple environmental stresses at the same time. 3. The core value of the comprehensive test chamber is to break through the limitations of single-factor environmental testing and provide a test method closer to the actual working conditions for product reliability evaluation.
2. Principle
3. The working principle of the comprehensive test chamber is based on the multiphysics coupling theory and environmental simulation technology. Its essence is to make the three environmental stresses of temperature, humidity and vibration act on the test product according to the predetermined law under controlled conditions, so as to stimulate and expose the potential defects that are difficult to appear under the action of a single stress.
From the perspective of thermodynamics, the temperature control system works together with the heater and the refrigeration system to achieve precise adjustment and rapid change of air temperature in the box. The air flows through a heater or evaporator driven by a fan, and after a thorough mixture, it enters the working chamber evenly to form the desired temperature field. Humidity control is based on the principle of adjusting the content of water vapor in the air, generating water vapor through the humidifier to increase humidity, reducing humidity through condensation and dehumidification of the refrigeration system, and maintaining the set relative humidity level with the feedback control of the humidity sensor.
At the heart of the vibration system is an electric vibration generator, which works on the principle of electromagnetic induction. When the drive coil is transmitted with alternating current in the magnetic field, it is affected by the Lorentz force and produces reciprocating motion, which drives the vibrating table connected to it to vibrate according to the set waveform, frequency and amplitude. Vibration parameters include frequency range, acceleration amplitude, displacement amplitude, and vibration waveform type, such as sinusoidal vibration, random vibration, shock response spectrum, etc.
The combined effect of the three stresses stems from their mutual coupling effect: the thermal expansion and contraction of the material caused by temperature change, which changes the dimensional accuracy and internal stress distribution of the structure; Humidity infiltration leads to moisture absorption expansion or deabsorption and contraction of the material, which affects the physical properties and interfacial bonding strength. Vibration stress causes alternating strain in the structure and causes fatigue accumulation. When the three act at the same time, thermal stress may accelerate moisture diffusion, moisture may reduce the fatigue resistance of the material, and vibration may promote crack propagation and accelerate moisture intrusion, forming a complex failure mechanism superposition.
3. Measurement method
3. The measurement method of the comprehensive test chamber involves the accurate detection and data collection of multiple physical quantities, and it is necessary to establish a complete measurement calibration system and test procedures to ensure the accuracy and repeatability of test conditions.
Temperature Measurement:The basic principle is to use the characteristics of platinum metal resistance value with temperature change, through a precision bridge or constant current source to measure the change of resistance value, and convert it into a temperature value after calibration. The temperature measurement points should be arranged in representative positions in the workspace, usually taking nine points of the studio volume for uniformity testing as specified in the standard. The temperature performance index includes temperature deviation, temperature fluctuation, and temperature uniformity, of which the temperature deviation refers to the difference between the set temperature and the measured average temperature at the center point, the temperature fluctuation refers to the change of temperature at any point in the working space in the stable state with time, and the temperature uniformity refers to the maximum difference between the instantaneous temperature of each measurement point in the working space in the stable state.
Humidity measurement:Humidity measurement mainly uses the dry and wet bulb method or electronic humidity sensor. The dry and wet bulb method is based on the difference between the dry bulb temperature and the wet bulb temperature, and the relative humidity value is obtained by checking the table or calculating, which is stable and reliable but the response is slow. Electronic humidity sensors are mostly capacitive or resistive moisture-sensitive components, which use the principle of dielectric constant or resistivity change after moisture absorption of moisture-sensitive materials to achieve rapid humidity measurement. The performance indexes of humidity measurement include humidity deviation, humidity fluctuation, and humidity uniformity, and the uniformity index is usually looser than that of temperature uniformity because the humidity field is significantly affected by temperature distribution.
Vibration measurement:The measurement of vibration parameters uses an accelerometer as a sensing element, commonly used piezoelectric accelerometer, its working principle is based on the piezoelectric effect, when the accelerometer moves with the vibrating table, the mass mass exerts an inertial force proportional to the acceleration to the piezoelectric element, generating a charge output proportional to the acceleration, and the acceleration signal is obtained after charge amplifier and signal conditioning. Vibration measurement requires frequency response analysis, distortion test and amplitude linearity test. Key indicators include frequency indication error, acceleration amplitude indication error, lateral vibration ratio, table acceleration uniformity, etc.
Comprehensive measurement method:3. The measurement of the comprehensive test chamber should consider the interaction between various physical quantities. The temperature sensor and humidity sensor should be arranged in a representative position near the vibrating table, which should not only avoid the impact of vibration on the reliability of the sensor connection, but also avoid the interference of the sensor itself on the vibration field. When conducting comprehensive condition measurement, the strategy of partition synchronous measurement is usually adopted, the temperature and humidity measurement system is continuously recorded, the vibration control system monitors the acceleration response at the same time, and the central data acquisition system processes the signals of each channel uniformly to ensure the synchronization of time and the consistency of data. The measurement cycle should be carried out in accordance with national metrology regulations or international standards, usually once a year, and key parameters or key tests can be verified during the period.
4. Influencing factors
3. The accuracy of the comprehensive environmental simulation and the reliability of the test results of the comprehensive test chamber are restricted by many factors, and an in-depth understanding of these influencing factors is of great significance for the correct use of equipment and scientific interpretation of test data.
Equipment Structure and Configuration:The structural design of the test chamber directly affects the uniformity and stability of the temperature and humidity field. The rationality of the air duct system determines the efficiency of air circulation, and the air supply mode of top air supply, side air supply or bottom air supply will affect the airflow organization and temperature distribution in the box. The connection between the shaker and the box is a key structural factor, and the flexible connecting film should not only ensure the sealing of the box, but also effectively isolate the transmission of vibration energy to the box, so as to prevent the resonance of the box from interfering with the test results. The installation methods of the shaker table include self-lifting, hydraulic lifting and gantry lifting, etc., and different methods have different effects on vibration isolation effect and space utilization.
Refrigeration and heating systems:The cooling capacity of the refrigeration system, the type of compressor, and the choice of refrigerant determine the minimum temperature and cooling rate that can be achieved by the chamber. Stacked refrigeration systems enable lower temperature ranges and faster temperature change rates, but with a corresponding increase in system complexity and energy consumption. The power density and thermal inertia of the heater affect the rate of rise and the ability to control temperature overshoot. The dynamic balance between cooling and heating determines the stability and accuracy of temperature control.
Humidification and dehumidification methods:The humidification method can be divided into two categories: steam humidification and spray humidification, which has fast response and high control accuracy, but needs to be equipped with a steam generator. Spray humidification is simple in structure, but may produce water droplets that affect the test sample. Dehumidification is mainly achieved through condensation of the refrigeration system, and the dehumidification capacity is closely related to the temperature and wind speed of the evaporator. The accuracy of humidity control is significantly affected by temperature fluctuations, and small changes in temperature can lead to significant fluctuations in relative humidity.
Vibration System Characteristics:The thrust level of the shaker determines the maximum acceleration and load capacity that can be achieved, and the thrust calculation formula is F = m × a, where F is the thrust, m is the sum of the mass of the moving part and the load mass, and a is the required acceleration. The frequency range of the shaker, the first-order resonant frequency, and the allowable eccentricity moment affect the fidelity of the vibration waveform and its adaptability to different loads. The size of the vibrating table and the distribution of connection points affect the ease of load installation and the uniformity of vibration transmission.
Control System Performance:The algorithm and parameter setting of the controller directly affect the stability and response speed of the temperature and humidity field. The advanced control system adopts PID adaptive algorithm or fuzzy control algorithm, which can adjust control parameters in real time according to the system state. The controller's sampling cycle, output resolution, and anti-interference capabilities also affect control accuracy. The synchronization of multi-channel data acquisition and the accuracy of signal processing algorithms determine the reliability of the final measurement results.
Load characteristics:The size, quality, heat capacity and heat generation of the test products had significant effects on the performance of the test chamber. Large heat capacity loads slow down the rate of temperature change and require longer settling times. The heating load cancels out the cooling capacity and may exceed the chamber's cooling capacity. The way the load is installed and the position of the center of mass affects the dynamic characteristics of the shaker and the uniformity of vibration distribution.
Environmental Conditions:The temperature, humidity and ventilation conditions of the test chamber installation environment directly affect the heat dissipation efficiency of the refrigeration system and the operational stability of the equipment. Too high ambient temperature can cause the condensation pressure of the refrigeration system to increase, reduce the cooling efficiency, and even trigger the compressor overheating protection. Environmental cleanliness affects the long-term stability of the sensor and the lifespan of moving parts.
5. Application
3. As a key equipment in the field of reliability testing, the comprehensive test chamber plays an irreplaceable role in product research and development, quality control and failure analysis in many industries.
Aerospace and military sector:This is the most widely and rigorously used field of the three comprehensive test chambers. Aircraft airborne equipment, missile guidance systems, satellite components, and aerospace electronics are subject to drastic temperature fluctuations from the ground to high altitude, high humidity environments, and continuous vibration loads during storage, transportation, and actual flight. 3. The comprehensive test can simulate the comprehensive environment of the aircraft at different altitudes, different climate regions and different power stages, effectively exposing potential defects such as virtual welding of components, poor material matching, and structural resonance. Military product standards such as the GJB150 series clearly stipulate that many environmental test projects require the use of comprehensive environmental testing methods.
Electronic Appliances and Information Communication:During transportation and use, electronic products such as mobile phones, computers, routers, and base station equipment not only face temperature cycles caused by day and night temperature differences and seasonal changes, but also suffer vibration excitation from transportation vibrations, fan vibrations, or user movements. Through three comprehensive tests, the functional stability of the product in the composite environment can be verified, and the structural design and material selection can be optimized. Especially for outdoor base station equipment, on-board electronic products and portable equipment, the three comprehensive tests have become an important part of product finalization.
Automotive Industry & Rail Transit:Automotive parts such as engine control units, sensors, instrument panels, connectors, etc., are subjected to engine vibration, road excitation, and high temperature and high humidity environments in the engine compartment during vehicle operation. 3. The comprehensive test can simulate the thermal cycle and vibration coupling conditions of the engine compartment, and find that the fatigue failure of electronic components and the poor contact of connectors are found. High-voltage components such as battery packs and motor controllers of new energy vehicles have higher requirements for comprehensive environmental adaptability, and their safety and reliability need to be verified through composite tests of temperature cycling, humidity penetration and random vibration.
New energy industry:Photovoltaic inverters, wind control systems, and energy storage equipment need to operate reliably for a long time in harsh outdoor environments. 3. The comprehensive test can simulate the comprehensive performance changes of photovoltaic modules under the temperature difference between day and night, moisture intrusion and wind-loaded vibration, and evaluate the long-term reliability of packaging materials and terminal blocks. By applying temperature cycling, humid and hot environment, and vibration stress at the same time, the structural integrity, connection reliability, and tightness of the cooling system of the battery module can be verified to avoid safety accidents during use.
Medical Device Industry:With the trend of portability and complexity of medical devices, their environmental adaptability requirements are increasing. Medical monitors, ultrasound diagnostic equipment, in vitro diagnostic instruments, etc. need to withstand temperature and humidity changes and vibration shocks during transportation and use. 3. The comprehensive test chamber can be used to verify the performance stability of the product in a comprehensive environment and ensure reliable operation under harsh conditions such as first aid, vehicle or field. Medical device standards such as GB/T 14710 and YY9706.111 clearly stipulate the requirements for environmental testing.
Research institutes and testing institutions:Testing centers, key laboratories and third-party testing institutions use the three comprehensive test chambers as the core equipment of reliability testing. These institutions use three comprehensive test chambers to carry out standard conformity testing, product certification testing, and failure analysis research. By undertaking comprehensive environmental tests of different industries and different types of products, we have accumulated a large amount of test data and analysis experience, providing support for quality improvement and technological progress in related industries.
Applications in special fields:The explosion-proof three-integrated test chamber is suitable for environmental adaptability verification in hazardous places where combustible gases or dust may exist, such as coal mining equipment, petrochemical instruments and explosion-proof electrical appliances. This specially designed test chamber adopts explosion-proof measures in terms of electrical system, temperature control and structural sealing to ensure that there is no ignition hazard while simulating harsh environments.
6. Summary
3. As the culmination of environmental simulation technology, the comprehensive test chamber represents the development direction of reliability test equipment from single-factor simulation to multi-factor composite simulation. It organically combines the three environmental stresses of temperature, humidity and vibration to construct test conditions closer to real working conditions, which provides an irreplaceable technical means for revealing the failure mechanism of the product under multiphysics coupling, evaluating the environmental adaptability of the product, and screening potential early faults.
By definition, the essence of the three comprehensive test chambers is a comprehensive simulation platform for multiple environmental stresses, and its core value is to achieve the test effect of 1+1+1>3, that is, the failure excitation capacity generated by the simultaneous action of three stresses is much higher than that of the superposition of single stresses. Its principle is based on the intersection of heat transfer, wet aerodynamics and mechanical vibration, and the test product is subjected to synergistic environmental loads by precisely controlling the temperature, humidity and vibration fields.
At the level of measurement methods, the accurate measurement and synchronous collection of temperature, humidity and vibration parameters are the basis for ensuring the effectiveness of the test, and it is necessary to establish a perfect measurement calibration system and data processing methods. The factors affecting the performance of the three comprehensive test chambers cover multiple dimensions such as equipment structure design, refrigeration and heating system, humidification and dehumidification methods, vibration system characteristics, control system performance, load characteristics and environmental conditions, which require equipment users to have systematic thinking in the process of use and maintenance, and comprehensively consider the synergistic effects of various factors.
In the application field, the three comprehensive test chambers have gradually expanded from the initial aerospace and military fields to important industries of the national economy such as electronic and electrical appliances, automobile industry, new energy, medical equipment, and scientific research and testing. With the continuous improvement of product complexity and reliability requirements, as well as the continuous emergence of new materials and processes, the importance of the three comprehensive test technologies will become increasingly prominent. In the future, the three comprehensive test chambers will develop in the direction of wider temperature range, faster temperature change rate, wider vibration frequency, higher control accuracy, and intelligence and networking, providing more solid technical support for product quality improvement and technological innovation in all walks of life.