Windshield glass crack characteristics are of great interest to vehicle manufacturers, safety eng... more Windshield glass crack characteristics are of great interest to vehicle manufacturers, safety engineers, and accident investigators, because they contain important information on energy mitigation, pedestrian protection, and accident reconstruction. We use the extended finite element method (XFEM) to analyze the model problem of low-speed head impact on a windshield plate. Both the radial crack and circumferential crack propagations are characterized.
Reconstruction of pedestrian-vehicle accident is a worldwide problem. Numerous previous studies h... more Reconstruction of pedestrian-vehicle accident is a worldwide problem. Numerous previous studies have been carried out on accidents with vehicular skid marks or definite pedestrian throw distances. However, little could be done if marks or throw distances cannot be obtained in accident reconstruction. This paper first describes the physical model of dynamic process of pedestrian head impact on windshield glazing. Some simplifications are made to obtain a better and more practical model, including discussing the support boundary conditions. Firstly, the paper modeled the relations between pedestrian impact speed and deflection of windshield glazing based on the impact dynamics and thin plate theory. Later, the relations of vehicle impact speed and deflection are discussed. Therefore, a model of vehicle impact speed versus deflection of windshield glazing is developed. The model is then verified by ten real-world accident cases to demonstrate its accuracy and reliability. This model provides investigators a new method to reconstruct pedestrian-vehicle accidents.
Windshield is one of the most important components in automobile to protect pedestrian and passen... more Windshield is one of the most important components in automobile to protect pedestrian and passenger, as well as enhance vehicle crashworthiness. The most widely used material for windshield is polyvinyl butyral (PVB) laminated glass. This paper uses both quasi-static compression and dynamic Split Hopkinson Pressure Bar (SHPB) compression experiments under different strain/loading rates to investigate the mechanical behavior of PVB laminated glass. Experimental results show that PVB laminated glass is a strong rate-dependent material with nonlinearity in its constitutive behavior under both quasi-static and dynamic loading circumstances. In quasi-static cases, major failure onset (MFO) strain increases with the loading rate while MFO stress remains the same; however MFO strain and stress will both increase in higher strain rates in dynamic loading. A constitutive model covering all strain/loading rates is then established based on Johnson–Cook model mathematically. Further, crack branching based on crack fractal theory is investigated and an explicit expression describing the crack velocity and number of crack branching is proposed. In addition, dynamic stress intensify factor is calculated to be β≈1.5 and an “impact caused brittleness” effect in PVB laminated material is discussed. Results can provide important experiment data and useful model to further research on vehicle crash safety.
During automotive related accidents, PVB plays an important role in both pedestrian and passenger... more During automotive related accidents, PVB plays an important role in both pedestrian and passenger protection as an interlayer of automotive windshield. In this paper, dynamic constitutive behavior of PVB material is thoroughly studied. Firstly, a set of dynamic compression impact experiments on PVB specimens using SHPB (Split Hopkinson Pressure Bar) method are conducted at strain rates from 700/s to 4500/s. Details of the constitutive response is analyzed based on the validation of experiment data. Stress-strain curve of PVB is then divided into two parts, i.e., "Compaction Stage" and "Hardening Stage". Dislocations and entanglements among molecules are major reasons for the two-stage phenomena. Constitutive behaviors are different in low and high speed impacts, leading to three times more energy absorption ability of PVB in high speed impact scenario. Further, data fitting models based on both MooneyeRivlin and Ogden Model are studied and then compared. MooneyeRivlin Model is found to be more appropriate to describe PVB material. Moreover, PVB is proved to be a rate-dependent material with the failure strength intensify factor b z 4. PVB material shows little viscoelasticity after comparison of the both models with and without the viscoelasticity part. Results offer critical experimental data, constitutive models and analysis of PVB material to further study of automotive crashworthiness and pedestrian/passenger protection.
Windshield glass crack characteristics are of great interest to vehicle manufacturers, safety eng... more Windshield glass crack characteristics are of great interest to vehicle manufacturers, safety engineers, and accident investigators, because they contain important information on energy mitigation, pedestrian protection, and accident reconstruction. We use the extended finite element method (XFEM) to analyze the model problem of low-speed head impact on a windshield plate. Both the radial crack and circumferential crack propagations are characterized.
Reconstruction of pedestrian-vehicle accident is a worldwide problem. Numerous previous studies h... more Reconstruction of pedestrian-vehicle accident is a worldwide problem. Numerous previous studies have been carried out on accidents with vehicular skid marks or definite pedestrian throw distances. However, little could be done if marks or throw distances cannot be obtained in accident reconstruction. This paper first describes the physical model of dynamic process of pedestrian head impact on windshield glazing. Some simplifications are made to obtain a better and more practical model, including discussing the support boundary conditions. Firstly, the paper modeled the relations between pedestrian impact speed and deflection of windshield glazing based on the impact dynamics and thin plate theory. Later, the relations of vehicle impact speed and deflection are discussed. Therefore, a model of vehicle impact speed versus deflection of windshield glazing is developed. The model is then verified by ten real-world accident cases to demonstrate its accuracy and reliability. This model provides investigators a new method to reconstruct pedestrian-vehicle accidents.
Windshield is one of the most important components in automobile to protect pedestrian and passen... more Windshield is one of the most important components in automobile to protect pedestrian and passenger, as well as enhance vehicle crashworthiness. The most widely used material for windshield is polyvinyl butyral (PVB) laminated glass. This paper uses both quasi-static compression and dynamic Split Hopkinson Pressure Bar (SHPB) compression experiments under different strain/loading rates to investigate the mechanical behavior of PVB laminated glass. Experimental results show that PVB laminated glass is a strong rate-dependent material with nonlinearity in its constitutive behavior under both quasi-static and dynamic loading circumstances. In quasi-static cases, major failure onset (MFO) strain increases with the loading rate while MFO stress remains the same; however MFO strain and stress will both increase in higher strain rates in dynamic loading. A constitutive model covering all strain/loading rates is then established based on Johnson–Cook model mathematically. Further, crack branching based on crack fractal theory is investigated and an explicit expression describing the crack velocity and number of crack branching is proposed. In addition, dynamic stress intensify factor is calculated to be β≈1.5 and an “impact caused brittleness” effect in PVB laminated material is discussed. Results can provide important experiment data and useful model to further research on vehicle crash safety.
During automotive related accidents, PVB plays an important role in both pedestrian and passenger... more During automotive related accidents, PVB plays an important role in both pedestrian and passenger protection as an interlayer of automotive windshield. In this paper, dynamic constitutive behavior of PVB material is thoroughly studied. Firstly, a set of dynamic compression impact experiments on PVB specimens using SHPB (Split Hopkinson Pressure Bar) method are conducted at strain rates from 700/s to 4500/s. Details of the constitutive response is analyzed based on the validation of experiment data. Stress-strain curve of PVB is then divided into two parts, i.e., "Compaction Stage" and "Hardening Stage". Dislocations and entanglements among molecules are major reasons for the two-stage phenomena. Constitutive behaviors are different in low and high speed impacts, leading to three times more energy absorption ability of PVB in high speed impact scenario. Further, data fitting models based on both MooneyeRivlin and Ogden Model are studied and then compared. MooneyeRivlin Model is found to be more appropriate to describe PVB material. Moreover, PVB is proved to be a rate-dependent material with the failure strength intensify factor b z 4. PVB material shows little viscoelasticity after comparison of the both models with and without the viscoelasticity part. Results offer critical experimental data, constitutive models and analysis of PVB material to further study of automotive crashworthiness and pedestrian/passenger protection.
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Papers by Yibing Li