Mechanical Mechanism Of Damage And Fracture Of Tempered Glass Under Impact Load

Tempered glass is widely used in engineering because of its excellent transparency and safety,but it is often impacted in use.According to the characteristics of impact load and the different mechanical model of tempered glass,tempered glass can be divided into two types under the actual service environment.The first type is that tempered glass is impacted by particles with smaller particle size At this time,the mechanical model of tempered glass is semi infinite body model,such as tempered glass in sandstorm.This kind of high-speed gas carries a large number of solid particles to impact the material repeatedly at a certain speed and angle is called erosion,which mainly causes the tempered glass to break at the micro level and forms material removal In Inner Mongolia,there are frequent sandstorms.The use and safety of tempered glass in this area are seriously affected by sand erosion.In the second case,the tempered glass is impacted by heavy objects with large particle size and certain mass.In this case,the impact load is large and the impact load range is large.At this time,the mechanical model of tempered glass is thin plate model,which is the main impact condition In order to cause the tempered glass to break at the macro level,it often breaks under the impact of falling rocks or objects blown down by strong wind in actual use.The broken tempered glass will threaten the safety of users.This project is supported by the National Natural Science Foundation of China（Grant No.:11662012）,and is based on the actual service environment of tempered glass in Inner Mongolia.The distribution rule of stress and strain field of tempered glass under the impact of particles and heavy objects is analyzed;the erosion test of tempered glass is carried out,and the mechanical mechanism of erosion damage of tempered glass is analyzed;the ball pressure impact test of tempered glass is carried out,and the mechanical mechanism of impact fracture of tempered glass is analyzed;the influence of erosion damage on the impact resistance of tempered glass is studied The fracture mechanism of tempered glass with erosion damage is analyzed.The main research contents are as follows:1. According to the division of impact velocity by impact dynamics,the range of impact velocity studied in this paper is discussed as the minimum velocity range and the initial subelastic velocity range;the relationship between impact load and impact velocity is analyzed,which shows that impact load is not only related to the velocity,mass and size of the impact object,but also related to the material constant of the impact object and the impacted object;three kinds of fracture modes of materials are described Three fracture criteria for brittle materials are analyzed,which provide theoretical basis for the subsequent analysis.2. The characteristics of the impact load of the particles with small particle size and the heavy objects with large particle size and certain mass when they impact the tempered glass are analyzed.According to the characteristics of the impact load,the mechanical model of the tempered glass under the condition of small load when the particles impact is analyzed is the semi infinite model.The semi infinite model theory of the surface concentrated force in the solid contact mechanics is applied to study The distribution law of the stress-strain field of the tempered glass under the impact of particles is studied.The mechanical model of the tempered glass under the condition of heavy impact is the thin plate model.The distribution law of the stress-strain field of the tempered glass under the impact of heavy impact is studied by using the theory of small deflection of the thin plate in elastic mechanics.3. Carry out a natural exposure test on tempered glass,place the tempered glass in an outdoor environment for one year of natural exposure,weigh and measure the two-dimensional shape after the test period,and study the damage of tempered glass in the actual environment;The sand-blast erosion test was carried out on the tempered glass by the airflow sand-blasting method.The effects of different erosion speeds and erosion angles on the erosion rate of the tempered glass were studied.Combining the erosion test results,the erosion of the tempered glass was analyzed using fracture mechanics The mechanical mechanism of damage is calculated by theoretical calculation of the impact of single sand particles on the tempered glass model at different impact speeds.The erosion removal volume increases with the increase of the erosion speed,and the maximum erosion removal volume occurs when the erosion speed is 31m/s,is 1.03×10^-5mm³,and the erosion removal volume grows faster at high erosion speed.The trend of calculation results and the trend of experimental results"the erosion rate increases with the erosion speed,and the erosion The erosion rate grows faster at high erosion speeds.”It is more consistent at medium and high erosion speeds.Increasing the erosion speed will cause the erosion particles to have a greater impact on the tempered glass surface.Loading increases the depth of indentation and radial cracks,which increases the volume of the exfoliated material of the tempered glass under repeated particle impacts,so the erosion rate increases with the increase of the erosion speed.Tempered glass at high erosion speeds The surface indentation depth and radial crack length increase faster,so the higher the erosion rate,the faster the erosion rate increases.The erosion rate of tempered glass increases with the increase of the erosion angle.The erosion mechanism is the principle of micro-cutting,and the erosion mechanism at high angles is indentation fracture.4. The impact test was carried out on the original toughened glass without damage in the later use process by using the ball pressure impact instrument.Combined with the test results,the fracture mechanism of toughened glass under impact load was studied by using the contact mechanics,stress-strain field analysis results and fracture criterion theory.The results show that when the toughened glass is not fractured under impact,the impact load on the contact surface boundary is generated the maximum tensile stress will produce circular microcracks on the surface of toughened glass specimens.In the impact test,the critical load of ring microcracks in toughened glass is 229.73n,and the point with the largest tensile deformation of rectangular toughened glass under the impact load at the center is the center of the lower surface,which is the starting point of fracture.The stress components of the toughened glass are onlyσ_xandσ_y,τ_xy,τ_xzandτ_yzare all 0.The toughened glass used in the experiment is near When the boundary fracture isσ_x=348.61MPa;σ_y=348.61MPa,its surface tensile strength is about 272MPa.The fracture process of toughened glass under impact load is divided into two stages:cracking and crack growth.The energy required for cracking is larger,and the energy required for crack growth is smaller.With the increase of impact speed,the proportion of cracking stage in the fracture process is larger and larger,so the impact load in the fracture stage is more and more with the increase of impact speed The impact load does not increase with the increase of impact speed,so the increase of impact load will slow down with the increase of impact speed.5. The impact test of toughened glass after sand erosion was carried out by ball impact tester.The impact of erosion damage on the impact resistance of toughened glass was studied.The results show that the impact resistance of toughened glass will be reduced by erosion damage.This is because with the increase of damage size,the stress required for damage extension and damage formation fracture will be reduced.When the applied stress is equal to that required for damage extension Under the stress,the damage will extend and form fracture.Therefore,the larger the initial damage size is,the smaller the external stress required for fracture is,and the worse the impact resistance of toughened glass is.