This paper introduces a kind of substitute bench testing method for vehicle application development and testing method of the test requirements,including battery fast conversion cycle test equipment,enter type incubat...This paper introduces a kind of substitute bench testing method for vehicle application development and testing method of the test requirements,including battery fast conversion cycle test equipment,enter type incubator,liquid-cooled machine and ancillary equipment composed of a set of test system,through the walk-in constant temperature box to simulate the new energy vehicles under different environmental conditions of the test requirements,Liquid-cooled machine and auxiliary parts to complete the battery thermal management system need cooling fluid conditions,the battery conversion cycle test equipment to simulate the dc fast charging way of filling pile,complete battery thermal management system test,shorten the filling fast charging time and improve battery fast charge security,for troubleshooting and data collection and analysis,Improve work efficiency,save costs,and eliminate customer anxiety about battery life and charging time.展开更多
The uniaxial compressive strength(UCS)of rocks is a vital geomechanical parameter widely used for rock mass classification,stability analysis,and engineering design in rock engineering.Various UCS testing methods and ...The uniaxial compressive strength(UCS)of rocks is a vital geomechanical parameter widely used for rock mass classification,stability analysis,and engineering design in rock engineering.Various UCS testing methods and apparatuses have been proposed over the past few decades.The objective of the present study is to summarize the status and development in theories,test apparatuses,data processing of the existing testing methods for UCS measurement.It starts with elaborating the theories of these test methods.Then the test apparatus and development trends for UCS measurement are summarized,followed by a discussion on rock specimens for test apparatus,and data processing methods.Next,the method selection for UCS measurement is recommended.It reveals that the rock failure mechanism in the UCS testing methods can be divided into compression-shear,compression-tension,composite failure mode,and no obvious failure mode.The trends of these apparatuses are towards automation,digitization,precision,and multi-modal test.Two size correction methods are commonly used.One is to develop empirical correlation between the measured indices and the specimen size.The other is to use a standard specimen to calculate the size correction factor.Three to five input parameters are commonly utilized in soft computation models to predict the UCS of rocks.The selection of the test methods for the UCS measurement can be carried out according to the testing scenario and the specimen size.The engineers can gain a comprehensive understanding of the UCS testing methods and its potential developments in various rock engineering endeavors.展开更多
With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure...With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure(CUCP)test cannot simulate the plastic yielding and instantaneous unloading process of supporting structure to rock.Thus,a high stress loading-instantaneous unloading confining pressure(HSL-IUCP)test method was proposed and applied by considering bolt’s fracture under stress.The wall thickness of confining pressure plates and the material of bolts were changed to realize different confin-ing pressure loading stiffness(CPLS)and lateral maximum allowable deformation(LMAD).The superio-rity of HSL-ICPU method is verified compared with CUCP.The rock failure mechanism caused by sudden failure of supporting structure is obtained.The results show that when CPLS increases from 1.35 to 2.33 GN/m,rock’s peak strength and elastic modulus increase by 25.18%and 23.70%,respectively.The fracture characteristics change from tensile failure to tensile-shear mixed failure.When LMAD decreases from 0.40 to 0.16 mm,rock’s residual strength,peak strain,and residual strain decrease by 91.80%,16.94%,and 21.92%,respectively,and post-peak drop modulus increases by 140.47%.The test results obtained by this method are closer to rock’s real mechanical response characteristics compared with CUCP.展开更多
It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mec...It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.展开更多
Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solv...Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solve the loading problems of large-tonnage cranes during testing, an equivalency test is proposed based on the similarity theory and BP neural networks. The maximum stress and displacement of a large bridge crane is tested in small loads, combined with the training neural network of a similar structure crane through stress and displacement data which is collected by a physics simulation progressively loaded to a static load test load within the material scope of work. The maximum stress and displacement of a crane under a static load test load can be predicted through the relationship of stress, displacement, and load. By measuring the stress and displacement of small tonnage weights, the stress and displacement of large loads can be predicted, such as the maximum load capacity, which is 1.25 times the rated capacity. Experimental study shows that the load reduction test method can reflect the lift capacity of large bridge cranes. The load shedding predictive analysis for Sanxia 1200 t bridge crane test data indicates that when the load is 1.25 times the rated lifting capacity, the predicted displacement and actual displacement error is zero. The method solves the problem that lifting capacities are difficult to obtain and testing accidents are easily possible when 1.25 times related weight loads are tested for large tonnage cranes.展开更多
Due to local uneven heating during the welding process,the residual stress of the structure after welding affects the reliability of it.In order to ensure the reliability,it is of great significance to test the residu...Due to local uneven heating during the welding process,the residual stress of the structure after welding affects the reliability of it.In order to ensure the reliability,it is of great significance to test the residual stress distribution of the welded joint.It has always been the focus to find a simple and feasible method for residual stress testing to quickly and accurately obtain the residual stress distribution of welded joints.The mechanical measurement method has high measurement accuracy,convenient and easy operation,but it will cause certain damage to the components.Physical measurement method can avoid damage to components,but its test cost is usually high,and its measurement accuracy can also be affected by the material microstructure characteristics of welded components.Based on the advantages and disadvantages of these two residual stress test methods,a modal test method is proposed.This method is a non-destructive measurement method.Based on the mathematical relationship between the residual stress of the welded structure and the natural frequency(mathematical model),the natural frequency is measured through the modal test to calculate the residual stress quickly.However,it is difficult to establish a mathematical model with this method,and it is not suitable for realization.展开更多
Based on the characteristics of pile-soil interaction and the Mohr-Coulomb strength theory,a new method of determining the side friction at a pile-soil interaction is proposed.Combined with the actual engineering case...Based on the characteristics of pile-soil interaction and the Mohr-Coulomb strength theory,a new method of determining the side friction at a pile-soil interaction is proposed.Combined with the actual engineering cases,the effectiveness of the analogue test method is verified by comparing it with the traditional anchor pile method and self-balanced method.Taking the self-balanced test of the bridge pile foundation in the Songhua River as an example,the conversion factor of sandy soil and weathered mudstone are confirmed by the analogue test method.The results show that the conversion factor of sandy soil and weathered mudstone in the Songhua River area should consider the geological conditions and the construction technology,etc.The standard values are relatively conservative.It is suggested that the engineering application should be properly revised.The recommended range of the conversion factor of sandy soil in this area is 0.65 to 0.85,and that of weathered mudstone is 1.0.展开更多
This paper presents a numerical analysis of a material test program investigating the crack opening properties of fibre reinforced concrete （FRC） round determinate panels （RDP）. The objective of this research is t...This paper presents a numerical analysis of a material test program investigating the crack opening properties of fibre reinforced concrete （FRC） round determinate panels （RDP）. The objective of this research is to set up a modified RDP test method to improve the current ASTM C1550 test method for FRC and fibre reinforced shotcrete （FRS） composite. By this test method, light small-diameter panels are applied and more crack information can be obtained by a new rotation angle measuring technique. It is shown that this modified test method can be used to effectively evaluate the crack opening resistance of FRC. The finite element analysis was then performed to clarify the crack propaga- tions and failure mode of FRC RDP panels. It helps establish a reasonable theoretical method to predict the structural response of RDP. combining with this modified testing technioue.展开更多
Experimental studies on the compressive behavior of composite laminates after low velocity impact was carried out with two test methods.One is SACMA Standard,and the other is a small dimensional specimen test method.I...Experimental studies on the compressive behavior of composite laminates after low velocity impact was carried out with two test methods.One is SACMA Standard,and the other is a small dimensional specimen test method.Impact damage distributions,compressive failure process after impact,quasi static indentation and compression of laminates with a hole were brought into comparison between these two test methods.The results showed that there is a great difference between these two test methods.Compressive behavior of laminates after impact varies with different test methods.Residual compressive strength of laminates after low velocity impact measured with SACMA Standard can reflect stiffness properties of composite resins more wholely than that measured with the other method can do.Small dimensional specimen test method should be improved on as an experimental standard of compressive strength after impact.展开更多
The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economic...The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength.Furthermore, the Poisson's ratio has no correlation with any of the direct and indirect test results.展开更多
Wet multi-plate clutches are relevant components of modern drivetrain applications,not only in terms of function but also safety and comfort.Especially at the beginning of their lifetime,distinct changes of the fricti...Wet multi-plate clutches are relevant components of modern drivetrain applications,not only in terms of function but also safety and comfort.Especially at the beginning of their lifetime,distinct changes of the friction behavior may occur and make the actuation of the clutch challenging.This transcript describes the typical running-in behavior of wet multi-plate clutches and gives a general definition for running-in of clutches.Moreover,a new test method to systematically investigate the running-in behavior of clutches is introduced.This test method contains a test procedure to characterize the running-in behavior on different load levels.Furthermore,a multi-stage procedure to evaluate and characterize the running-in behavior of clutches with mathematical approaches and new characteristic values is given.The quality of the test method is demonstrated on the example of three different tribological systems from dual clutch transmissions(DCT)and automatic transmissions(AT)application using paper friction linings.展开更多
Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application...Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.展开更多
The deviations of trajectory and attitude angle for internal store separation are evaluated by two wind tunnel test methods.One is the Freedrop Test(FDT),which is known as unsteady and time-dependent method of scaled ...The deviations of trajectory and attitude angle for internal store separation are evaluated by two wind tunnel test methods.One is the Freedrop Test(FDT),which is known as unsteady and time-dependent method of scaled model.The other is the Captive Trajectory System(CTS)test,which is usually regarded as a quasi-steady and time-averaged test technology.The result shows that there is a streamwise adverse pressure gradient on the cavity resulting in a nose-up pitching moment coefficient(>0)acting on the store model.When the initial pitch angular velocity is 0,the store exits the shear-layer with a nose-up pitch attitude causing the store to climb back towards and collide with the aircraft.However,the store passes through the shear-layer into the freestream with a nose-down pitch,which causes a successful separation event when the initial pitch angular velocity<0.The pitch angle obtained by unsteady test method is different from that by quasisteady test method.The time-dependent test includes the aerodynamic force induced by pitch angular velocity whereas the time-averaged method(CTS)cannot reflect the effect of unsteady aerodynamic force.The deviation of vertical displacement is not obvious for FDT and CTS test since the store has an initial vertical velocity,which is dominant for the vertical displacement.This means that the highly unsteady flow can create unpredictability in aerodynamic pitching moment of the store,which can lead to the deviation of pitch angle for internal store separation.展开更多
Combined with the tire dynamics theoretical model,a rapid test method to obtain tire lateral and longitudinal both steady-state and transient characteristics only based on the tire quasi-steady-state test results is p...Combined with the tire dynamics theoretical model,a rapid test method to obtain tire lateral and longitudinal both steady-state and transient characteristics only based on the tire quasi-steady-state test results is proposed.For steady state data extraction,the test time of the rapid test method is half that of the conventional test method.For transient tire characteristics the rapid test method omits the traditional tire test totally.At the mean time the accuracy of the two method is much closed.The rapid test method is explained theoretically and the test process is designed.The key parameters of tire are extracted and the comparison is made between rapid test and traditional test method.The result show that the identification accuracy based on the rapid test method is almost equal to the accuracy of the conventional one.Then,the heat generated during the rapid test method and that generated during the conventional test are calculated separately.The comparison shows that the heat generated during the rapid test is much smaller than the heat generated during the conventional test process.This benefits to the reduction of tire wear and the consistency of test results.Finally,it can be concluded that the fast test method can efficiently,accurately and energy-efficiently measure the steady-state and transient characteristics of the tire.展开更多
The factors influencing the permeability coefficient of gravelly soils used for the development of embankment dams(core wall)are analyzed.Such factors include(but are not limited to)soil size,anisotropy,density and bo...The factors influencing the permeability coefficient of gravelly soils used for the development of embankment dams(core wall)are analyzed.Such factors include(but are not limited to)soil size,anisotropy,density and boundary effects.A review of the literature is conducted and new directions of research are proposed.In such a framework,it is shown that gravelly soil with controlled density and vertical stress should be used to optimize the measurement of the vertical and horizontal permeability coefficients,respectively.展开更多
According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high sp...According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.展开更多
The depth of penetration(DOP)method is a well-known ballistic test method for characterisation and ranking of ceramic armour materials.The ceramic tile is bonded to a backing material of semi-infinite thickness,and th...The depth of penetration(DOP)method is a well-known ballistic test method for characterisation and ranking of ceramic armour materials.The ceramic tile is bonded to a backing material of semi-infinite thickness,and the penetration depth of the projectile gives a measure of the performance of the ceramic.There is,however,an inherent variability in the results from this test method.In this work,the accuracy and the variability of the DOP method has been investigated in a round robin exercise.Six ballistic test centres took part in the exercise.A test protocol was developed,in which the threat type(projectile and impact conditions)and a procedure on how to prepare the targets were specified.The targets consisted of alumina tiles of two different thicknesses that were bonded to polycarbonate backing cubes.Two different 7.62 mm armour piercing projectiles were employed;one with a hard steel core and one with a tungsten carbide core.The projectiles and the other materials all came from single material batches in order to avoid batch-to-batch variations in material properties.These materials were distributed between the ballistic test centres.The test results of the different ballistic test facilities were collected and compared.There was not a lot of variation between the average DOP values obtained at each laboratory,but the variation in penetration depth between shots was high.The consequence of this variation may be less confidence in the test results,and a statistical method was used to evaluate the required number of tests that are sufficient to obtain an average result with high confidence.In most cases,the required number of tests is much higher than what is practically feasible.This work was conducted as part of the European Defence Agency-project CERAMBALL.展开更多
Test methods for hot abrasion resistance of refractories in China and overseas were briefly introduced. A new test method for hot abrasion resistance was researched. The new method inherits test principle of cold abra...Test methods for hot abrasion resistance of refractories in China and overseas were briefly introduced. A new test method for hot abrasion resistance was researched. The new method inherits test principle of cold abrasion resistance in Chinese standard totally, adopts compressed air pre-heating and electricity heating sam- ples, and is featured with complete structure, good con- trollability, simple operation, and small size. The characteristics and operating procedure of HAT-14A tester were introduced. The hot abrasion resistance of various refractories at different temperatures was tested.展开更多
In this work,the factors and parameters of a test method on abrasion resistance at elevated temperatures were discussed and researched.First of all,the precision tests of the test method on abrasion resistance at elev...In this work,the factors and parameters of a test method on abrasion resistance at elevated temperatures were discussed and researched.First of all,the precision tests of the test method on abrasion resistance at elevated temperatures were conducted in 8 laboratories.The results such as the standard deviation and reproducibility show good repeatability and reliability.The relationship between the stability of refractory performance and the standard deviation of their wear value was analyzed.Then the impact of the heat treatment condition of unshaped refractories and oxidation of SiC sand as abrasive on the lost volume of the tested specimens was researched.展开更多
文摘This paper introduces a kind of substitute bench testing method for vehicle application development and testing method of the test requirements,including battery fast conversion cycle test equipment,enter type incubator,liquid-cooled machine and ancillary equipment composed of a set of test system,through the walk-in constant temperature box to simulate the new energy vehicles under different environmental conditions of the test requirements,Liquid-cooled machine and auxiliary parts to complete the battery thermal management system need cooling fluid conditions,the battery conversion cycle test equipment to simulate the dc fast charging way of filling pile,complete battery thermal management system test,shorten the filling fast charging time and improve battery fast charge security,for troubleshooting and data collection and analysis,Improve work efficiency,save costs,and eliminate customer anxiety about battery life and charging time.
基金the National Natural Science Foundation of China(Grant Nos.52308403 and 52079068)the Yunlong Lake Laboratory of Deep Underground Science and Engineering(No.104023005)the China Postdoctoral Science Foundation(Grant No.2023M731998)for funding provided to this work.
文摘The uniaxial compressive strength(UCS)of rocks is a vital geomechanical parameter widely used for rock mass classification,stability analysis,and engineering design in rock engineering.Various UCS testing methods and apparatuses have been proposed over the past few decades.The objective of the present study is to summarize the status and development in theories,test apparatuses,data processing of the existing testing methods for UCS measurement.It starts with elaborating the theories of these test methods.Then the test apparatus and development trends for UCS measurement are summarized,followed by a discussion on rock specimens for test apparatus,and data processing methods.Next,the method selection for UCS measurement is recommended.It reveals that the rock failure mechanism in the UCS testing methods can be divided into compression-shear,compression-tension,composite failure mode,and no obvious failure mode.The trends of these apparatuses are towards automation,digitization,precision,and multi-modal test.Two size correction methods are commonly used.One is to develop empirical correlation between the measured indices and the specimen size.The other is to use a standard specimen to calculate the size correction factor.Three to five input parameters are commonly utilized in soft computation models to predict the UCS of rocks.The selection of the test methods for the UCS measurement can be carried out according to the testing scenario and the specimen size.The engineers can gain a comprehensive understanding of the UCS testing methods and its potential developments in various rock engineering endeavors.
基金the National Natural Science Foundation of China(Nos.52374218,52174122 and 52374094)Outstanding Youth Fund of Shandong Natural Science Foundation(No.ZR2022YQ49)Taishan Scholar Project in Shandong Province(Nos.tspd20210313 and tsqn202211150).
文摘With the increase of underground engineering construction depth,the phenomenon of surrounding rock sudden failure caused by supporting structure failure occurs frequently.The conventional unloading con-fining pressure(CUCP)test cannot simulate the plastic yielding and instantaneous unloading process of supporting structure to rock.Thus,a high stress loading-instantaneous unloading confining pressure(HSL-IUCP)test method was proposed and applied by considering bolt’s fracture under stress.The wall thickness of confining pressure plates and the material of bolts were changed to realize different confin-ing pressure loading stiffness(CPLS)and lateral maximum allowable deformation(LMAD).The superio-rity of HSL-ICPU method is verified compared with CUCP.The rock failure mechanism caused by sudden failure of supporting structure is obtained.The results show that when CPLS increases from 1.35 to 2.33 GN/m,rock’s peak strength and elastic modulus increase by 25.18%and 23.70%,respectively.The fracture characteristics change from tensile failure to tensile-shear mixed failure.When LMAD decreases from 0.40 to 0.16 mm,rock’s residual strength,peak strain,and residual strain decrease by 91.80%,16.94%,and 21.92%,respectively,and post-peak drop modulus increases by 140.47%.The test results obtained by this method are closer to rock’s real mechanical response characteristics compared with CUCP.
基金supported by the Fundamental Research Funds for the Central Universities(No.YX2010-20)the Open Projects Foundation of Key Laboratory of Soil and Water Conservation & Desertification Combat (Beijing ForestryUniversity), Ministry of Education of P.R. China (No.201002) the National Natural Science Foundation of China (No. 31570708, No.30901162)
文摘It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.
基金Supported by National "Twelfth Five-Year" Plan for Science&Technology Support of China(Grant No.2011BAK06B05)National High-tech Research and Development Program of China(863 Program,Grant No.2013AA040203)Shanxi Scholarship Council of China(Grant No.2015-088)
文摘Static load tests are an important means of supervising and detecting a crane＇s lift capacity. Due to space restrictions, however, there are difficulties and potential danger when testing large bridge cranes. To solve the loading problems of large-tonnage cranes during testing, an equivalency test is proposed based on the similarity theory and BP neural networks. The maximum stress and displacement of a large bridge crane is tested in small loads, combined with the training neural network of a similar structure crane through stress and displacement data which is collected by a physics simulation progressively loaded to a static load test load within the material scope of work. The maximum stress and displacement of a crane under a static load test load can be predicted through the relationship of stress, displacement, and load. By measuring the stress and displacement of small tonnage weights, the stress and displacement of large loads can be predicted, such as the maximum load capacity, which is 1.25 times the rated capacity. Experimental study shows that the load reduction test method can reflect the lift capacity of large bridge cranes. The load shedding predictive analysis for Sanxia 1200 t bridge crane test data indicates that when the load is 1.25 times the rated lifting capacity, the predicted displacement and actual displacement error is zero. The method solves the problem that lifting capacities are difficult to obtain and testing accidents are easily possible when 1.25 times related weight loads are tested for large tonnage cranes.
基金Project was supported by the National Natural Science Foundation of China(Grant No.52165034)Science and Technology Programs of Inner Mongolia(Grant No.2020GG0301)+1 种基金Natural Science Foundation of Inner Mongolia Autonomous Region(Grant No.2019MS05061)Scientific Research Projects of Higher Education of Inner Mongolia Autonomous Region Institutions(Grant No.NJZY20066).
文摘Due to local uneven heating during the welding process,the residual stress of the structure after welding affects the reliability of it.In order to ensure the reliability,it is of great significance to test the residual stress distribution of the welded joint.It has always been the focus to find a simple and feasible method for residual stress testing to quickly and accurately obtain the residual stress distribution of welded joints.The mechanical measurement method has high measurement accuracy,convenient and easy operation,but it will cause certain damage to the components.Physical measurement method can avoid damage to components,but its test cost is usually high,and its measurement accuracy can also be affected by the material microstructure characteristics of welded components.Based on the advantages and disadvantages of these two residual stress test methods,a modal test method is proposed.This method is a non-destructive measurement method.Based on the mathematical relationship between the residual stress of the welded structure and the natural frequency(mathematical model),the natural frequency is measured through the modal test to calculate the residual stress quickly.However,it is difficult to establish a mathematical model with this method,and it is not suitable for realization.
基金The National Key Research and Development Program(No.2017YFC0703408)the National Natural Science Foundation of China(No.51478109,51678145,51878160)
文摘Based on the characteristics of pile-soil interaction and the Mohr-Coulomb strength theory,a new method of determining the side friction at a pile-soil interaction is proposed.Combined with the actual engineering cases,the effectiveness of the analogue test method is verified by comparing it with the traditional anchor pile method and self-balanced method.Taking the self-balanced test of the bridge pile foundation in the Songhua River as an example,the conversion factor of sandy soil and weathered mudstone are confirmed by the analogue test method.The results show that the conversion factor of sandy soil and weathered mudstone in the Songhua River area should consider the geological conditions and the construction technology,etc.The standard values are relatively conservative.It is suggested that the engineering application should be properly revised.The recommended range of the conversion factor of sandy soil in this area is 0.65 to 0.85,and that of weathered mudstone is 1.0.
基金Supported by the National Natural Science Foundation of China (50708084)Wuhan Chenguang Science and Technology Project for Young Experts (20035002016-30)
文摘This paper presents a numerical analysis of a material test program investigating the crack opening properties of fibre reinforced concrete （FRC） round determinate panels （RDP）. The objective of this research is to set up a modified RDP test method to improve the current ASTM C1550 test method for FRC and fibre reinforced shotcrete （FRS） composite. By this test method, light small-diameter panels are applied and more crack information can be obtained by a new rotation angle measuring technique. It is shown that this modified test method can be used to effectively evaluate the crack opening resistance of FRC. The finite element analysis was then performed to clarify the crack propaga- tions and failure mode of FRC RDP panels. It helps establish a reasonable theoretical method to predict the structural response of RDP. combining with this modified testing technioue.
文摘Experimental studies on the compressive behavior of composite laminates after low velocity impact was carried out with two test methods.One is SACMA Standard,and the other is a small dimensional specimen test method.Impact damage distributions,compressive failure process after impact,quasi static indentation and compression of laminates with a hole were brought into comparison between these two test methods.The results showed that there is a great difference between these two test methods.Compressive behavior of laminates after impact varies with different test methods.Residual compressive strength of laminates after low velocity impact measured with SACMA Standard can reflect stiffness properties of composite resins more wholely than that measured with the other method can do.Small dimensional specimen test method should be improved on as an experimental standard of compressive strength after impact.
基金CDC/NIOSH for their partial funding of this work
文摘The difficulties associated with performing direct compression strength tests on rocks lead to the development of indirect test methods for the rock strength assessment. Indirect test methods are simple, more economical, less time-consuming, and easily adaptable to the field. The main aim of this study was to derive correlations between direct and indirect test methods for basalt and rhyolite rock types from Carlin trend deposits in Nevada. In the destructive methods, point load index, block punch index, and splitting tensile strength tests are performed. In the non-destructive methods, Schmidt hammer and ultrasonic pulse velocity tests are performed. Correlations between the direct and indirect compression strength tests are developed using linear and nonlinear regression analysis methods. The results show that the splitting tensile strength has the best correlation with the uniaxial compression strength.Furthermore, the Poisson's ratio has no correlation with any of the direct and indirect test results.
基金The presented results are based on the research project FVA no.343/Ⅲ undertaken by the Research Association for Drive Technology e.V.(FVA).
文摘Wet multi-plate clutches are relevant components of modern drivetrain applications,not only in terms of function but also safety and comfort.Especially at the beginning of their lifetime,distinct changes of the friction behavior may occur and make the actuation of the clutch challenging.This transcript describes the typical running-in behavior of wet multi-plate clutches and gives a general definition for running-in of clutches.Moreover,a new test method to systematically investigate the running-in behavior of clutches is introduced.This test method contains a test procedure to characterize the running-in behavior on different load levels.Furthermore,a multi-stage procedure to evaluate and characterize the running-in behavior of clutches with mathematical approaches and new characteristic values is given.The quality of the test method is demonstrated on the example of three different tribological systems from dual clutch transmissions(DCT)and automatic transmissions(AT)application using paper friction linings.
基金supported by SGCC Scientific and Technological Project(52110116004W)
文摘Firstly, relevant stress properties of millisecond level breaking process and microsecond level commutation process of hybrid HVDC circuit breaker are studied in detail on the basis of the analysis for the application environment and topological structure and operating principles of hybrid circuit breakers, and key stress parameters in transient state process of two time dimensions are extracted. The established digital simulation circuit for PSCAD/EMTDC device-level operation of the circuit breaker has verified the stress properties of millisecond level breaking process and microsecond level commutation process. Then, equivalent test method, circuits and parameters based on LC power supply are proposed on the basis of stress extraction. Finally, the results of implemented breaking tests for complete 200 kV circuit breaker, 100 kV and 50 kV circuit breaker units, as well as single power electronic module have verified the accuracy of the simulation circuit and mathematical analysis. The result of this paper can be a guide to electrical structure and test system design of hybrid HVDC circuit breaker.
文摘The deviations of trajectory and attitude angle for internal store separation are evaluated by two wind tunnel test methods.One is the Freedrop Test(FDT),which is known as unsteady and time-dependent method of scaled model.The other is the Captive Trajectory System(CTS)test,which is usually regarded as a quasi-steady and time-averaged test technology.The result shows that there is a streamwise adverse pressure gradient on the cavity resulting in a nose-up pitching moment coefficient(>0)acting on the store model.When the initial pitch angular velocity is 0,the store exits the shear-layer with a nose-up pitch attitude causing the store to climb back towards and collide with the aircraft.However,the store passes through the shear-layer into the freestream with a nose-down pitch,which causes a successful separation event when the initial pitch angular velocity<0.The pitch angle obtained by unsteady test method is different from that by quasisteady test method.The time-dependent test includes the aerodynamic force induced by pitch angular velocity whereas the time-averaged method(CTS)cannot reflect the effect of unsteady aerodynamic force.The deviation of vertical displacement is not obvious for FDT and CTS test since the store has an initial vertical velocity,which is dominant for the vertical displacement.This means that the highly unsteady flow can create unpredictability in aerodynamic pitching moment of the store,which can lead to the deviation of pitch angle for internal store separation.
基金Supported by National Natural Science Foundation of China(Grant No.51775224).
文摘Combined with the tire dynamics theoretical model,a rapid test method to obtain tire lateral and longitudinal both steady-state and transient characteristics only based on the tire quasi-steady-state test results is proposed.For steady state data extraction,the test time of the rapid test method is half that of the conventional test method.For transient tire characteristics the rapid test method omits the traditional tire test totally.At the mean time the accuracy of the two method is much closed.The rapid test method is explained theoretically and the test process is designed.The key parameters of tire are extracted and the comparison is made between rapid test and traditional test method.The result show that the identification accuracy based on the rapid test method is almost equal to the accuracy of the conventional one.Then,the heat generated during the rapid test method and that generated during the conventional test are calculated separately.The comparison shows that the heat generated during the rapid test is much smaller than the heat generated during the conventional test process.This benefits to the reduction of tire wear and the consistency of test results.Finally,it can be concluded that the fast test method can efficiently,accurately and energy-efficiently measure the steady-state and transient characteristics of the tire.
基金The work is supported by National Key Research and Development Program of China(No.2017YFC0404803)Guizhou High-Level Innovative Talents Project[2018](No.5630)+2 种基金Guizhou Science and Support[2019](No.2869)State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(No.SKL2020ZY09)Science and Technology Project of Huaneng Group Headquarters(HNKJ17-H18).
文摘The factors influencing the permeability coefficient of gravelly soils used for the development of embankment dams(core wall)are analyzed.Such factors include(but are not limited to)soil size,anisotropy,density and boundary effects.A review of the literature is conducted and new directions of research are proposed.In such a framework,it is shown that gravelly soil with controlled density and vertical stress should be used to optimize the measurement of the vertical and horizontal permeability coefficients,respectively.
文摘According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.
基金conducted as part of the European Defence Agency-project CERAMBALL,contract number B 1091 GEM1 GP
文摘The depth of penetration(DOP)method is a well-known ballistic test method for characterisation and ranking of ceramic armour materials.The ceramic tile is bonded to a backing material of semi-infinite thickness,and the penetration depth of the projectile gives a measure of the performance of the ceramic.There is,however,an inherent variability in the results from this test method.In this work,the accuracy and the variability of the DOP method has been investigated in a round robin exercise.Six ballistic test centres took part in the exercise.A test protocol was developed,in which the threat type(projectile and impact conditions)and a procedure on how to prepare the targets were specified.The targets consisted of alumina tiles of two different thicknesses that were bonded to polycarbonate backing cubes.Two different 7.62 mm armour piercing projectiles were employed;one with a hard steel core and one with a tungsten carbide core.The projectiles and the other materials all came from single material batches in order to avoid batch-to-batch variations in material properties.These materials were distributed between the ballistic test centres.The test results of the different ballistic test facilities were collected and compared.There was not a lot of variation between the average DOP values obtained at each laboratory,but the variation in penetration depth between shots was high.The consequence of this variation may be less confidence in the test results,and a statistical method was used to evaluate the required number of tests that are sufficient to obtain an average result with high confidence.In most cases,the required number of tests is much higher than what is practically feasible.This work was conducted as part of the European Defence Agency-project CERAMBALL.
文摘Test methods for hot abrasion resistance of refractories in China and overseas were briefly introduced. A new test method for hot abrasion resistance was researched. The new method inherits test principle of cold abrasion resistance in Chinese standard totally, adopts compressed air pre-heating and electricity heating sam- ples, and is featured with complete structure, good con- trollability, simple operation, and small size. The characteristics and operating procedure of HAT-14A tester were introduced. The hot abrasion resistance of various refractories at different temperatures was tested.
文摘In this work,the factors and parameters of a test method on abrasion resistance at elevated temperatures were discussed and researched.First of all,the precision tests of the test method on abrasion resistance at elevated temperatures were conducted in 8 laboratories.The results such as the standard deviation and reproducibility show good repeatability and reliability.The relationship between the stability of refractory performance and the standard deviation of their wear value was analyzed.Then the impact of the heat treatment condition of unshaped refractories and oxidation of SiC sand as abrasive on the lost volume of the tested specimens was researched.
