Design and Application of Automatic Calibration Device for Multi-Channel Resistance Strain Gauge Indicator

In this paper, an automatic calibration device for multi-channel resistance strain gauge indicator is designed and its applicability and measurement accuracy are verified at laboratory. The calibration done by original resistance bridge calibrator is time-consuming for its manual operation and complex calibration process. With the intent to increase calibration efficiency, an automatic channel switch device was developed, and the resistance bridge calibrator was automated. The designed calibration device is completely computer controlled enabling a sequence of unmanned measurements. The calibration device was verified at laboratory that the maximum of error is 0.072%. It was applied to calibrate a 60-channel resistance strain gage indicator to approve its practical applicability. The result shows that the designed calibration device can realize automatic calibration and the efficiency is increased by 40%.

Experimental Cutting Force Properties on Interpenetrating Network Composites with Double Metal Phases

Cutting properties of interpenetrating network composites are important to ensure machining quality. The cutting force signals were measured by resistance strain gage of octagonal ring style and data acquisition and processing system. The results show that the cutting forces are affected by cutting conditions. To average cutting forces of interpenetrating network composites, the laws are basically consistent with that of the traditional materials. Because of the reinforced phase, the sudden cutting forces arise in cutting process whose values are relate to cutting parameters and reinforced phase dimensions.

Stress State Evaluation in Complete Denture by Electrical Resistance Strain Gage

Total dentures are made of acrylic resins and artificial teeth. Among the prevalent fracture types of the dentures, 29% was a mid-line fracture, in which 68% were observed in maxillary complete dentures and 28% in mandibular complete dentures. Due to the large number of failures recorded on the maxillary dentures, several studies were conducted to establish the causes that produce these failures but also to find solutions for their prevention. One source of information about the strength of a maxillary denture under the applied load, is represented by the establishment of the stress and strain state during the loading. Different methods have been used for investigating the strain or stress distribution during deformation of dentures. The purpose of this paper is to evaluate the stress and strain state of a maxillary denture loaded in compression until the final fracture. For this study, electrical resistance strain gage were used for evaluation the strain and stress distribution in the maxillary denture made of different acrylic resins. Based on observations from practice, the strain gages were applied on the middle line of the denture at the base of the incisors and respectively on the sides of the denture, under molars. The dentures were loaded until failure and were registered the strains in the located strain gages. Also, for each type of acrylic resin were determined separately the mechanical properties of elasticity and strength. Based on the tests conducted were determined the critical stress and strain in the areas of interest. In all the tests carried out the fracture occurred in the median area of the denture and the crack was initiated between the incisor teeth. The stress and strain field associated with the crack initiation mode showed a strong influence of geometry on the fracture strength of denture. Also the type of acrylic resin has a significant effect on the fracture strength of complete denture either by strength capacity but especially by their ability to elasticity. Based on this analysis have been established new criteria for selection of acrylic resins, not only for aesthetic reasons but also for elasticity and strength reasons.

Experimental Research on Transmission Characteristics of Working Mechanisms for Servo Mechanical Presses

In order to analyze the transmission characteristics of the knuckle-triangle working mechanism for servo mechanical presses, an experimental prototype was set up, and a wireless measurement system was developed, to measure the kinematic and dynamic characteristics of the working mechanism. The working principle of the dynamic measurement was expressed. The forming force applied to the slide was measured by a donut-shaped load cell. The driving torque applied to the crank was measured by a resistance strain gage. To collect the testing signals of the forming force and driving torque conveniently and synchronously, a wireless measure system based on WiFi is proposed. Moreover, when the input crank rotates at different angular speeds, the slide stroke curves were measured by a grating scale. The experimental results showed that the developed system can perform wireless measurement, and provide experimental basis for the analysis of kinematic and dynamic characteristics of the working mechanism with servo input.

Study on Fiber Bragg Grating Monitoring Technique and its Application in Bridge Strengthening

In engineering structures, it is a new approach to evaluate the structural health situation by use of optic fiber sensor. In this paper, a standard specimen beam, 200mm×300mm×3000mm, is chosen and the comparative experiment is executed for strain testing by FBG sensors and vibrating wire sensors which were widely used in bridge health monitoring. Experimental results show that the FBG sensors have a higher measurement precision, higher linearity and better noise resistance. Then we use traditional electrical resistance strain gage to calibrate the FBG sensors and obtain the strain degree of sensitivity, and apply them into bridge strengthening in the Wuhuang Highway in order to collect the strains of reinforcement bar in the deck pavement and the beams before and after the bridge strengthening. The above work is also to evaluate the effects of strengthening projects and carry out long-term structural health monitoring. The monitoring results show that the safety condition can be monitored conveniently with the FBG sensors testing system whose durability and stability can satisfy the need of bridge health monitoring. Finally, we also discuss the key problems and practical approaches in structural health monitoring process by use of embedded FBG sensors.

Development of Wireless Resistance Strain Gage Based on ATmega16

Measuring a large amount of parameters of work piece, resistance strain gage will have to use many resistive signal conversion boxes and long electric wires. Data acquisition becomes slow, inaccurate and discontinuous. Disorder and thermal of contact potential in the contacts affect the measurement signal and converting precision. In this paper, a wireless portable resistance strain gage is developed. ATmega16 is an 8-bit embedded and high-speed AVR single-chip microcomputer with 16k FlASH, and that is the core of system. Amplifier is designed to amplify and filter micro-voltage signals to improve measure accuracy. Wireless Bluetooth technology links ATmega16 and PC. Visual Basic software displays and processes data from ATmega16 in real time. This system is small in size and highly reliable, strong anti-interference ability and better economic performance.

A CALIBRATION METHOD OF MECHANICAL STRAINS FROM A TEMPERATURE-COMPENSATING FBG SENSOR

The sensitivity of a temperature-compensating fiber Bragg grating (FBG) sensor which has different FBGs in one fiber line was analyzed for the real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various heating rates and temperature range. The results were compared with those of an electrical resistance strain gage. A considerable delay in the strain measurement by the double FBG sensor during the heating process was shown, which could be quantified for the strain compensation by the introduction of a strain retardation factor to the FBG sensor.

Application of a Temperature-Compensating FBG Sensor to Strain Measurement

A temperature-compensating fiber Bragg grating(FBG) sensor having two different FBGs in one fiber line was applied to the real time measurement of mechanical normal strain in structures. Measurement of mechanical strains of the aluminum beam surface by the double FBG sensor was performed under various thermal conditions, which was compared with results of electrical resistance strain gage. The FBG sensor fabricated in this study could detect accurately values of mechanical strains without containing any thermal strain component.