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| 1 | A temperature/strain-rate-dependent finite deformation constitutive and failure model for solid propellants显示文摘The stress-strain response under progressive damage and the ultimate failure of solid propellants are two key issues affecting the integrity of solid rocket motors.Previous research primarily focused on the progressive damage in solid propellants during production and storage.However,they failed to take the temperature/strain-rate-dependent ultimate failures into consideration.The failure strains of solid propellants are experimentally observed to show strong temperature/strain-rate dependence and exhibit an abnormal evolution at low and high temperatures,respectively.With increasing loading strain rate,the failure strains decrease at low temperatures near the glass transition temperature(T_g)but increase at high temperatures far above T_(g).In this study,we introduce the glassy and rubbery failure criteria based on strain energy densities at ultralow and ultrahigh temperatures,respectively,into a viscoelastic constitutive model and build a unified model for the progressive damage and the ultimate failure of solid propellants.With the introduction of these two additional criterion parameters,the developed model can effectively predict the yield-type stress-strain responses,microscopic damage-induced volume dilatations,and temperature/strain-ratedependent ultimate failures of the solid propellants by comparing the model predictions with the experimental results.The competition between the glassy failure and the rubbery failure results in the propellants exhibiting a maximum break strain near the glass transition temperature.Consequently,when the strain rate is increased,the propellants exhibit a predominantly glassy response,which shifts the failure envelope toward a higher temperature.This induces an abnormal evolution of failure strains by making the propellants stretchable at high temperatures and brittle at low temperatures. | Ming Lei Erhao Chen Zeang Zhao Lihua Wen Jinyou Xiao Xiao Hou | 2023 | Science China(Physics,Mechanics & Astronomy)2023，66，9： | 1 |
| 2 | A novel hybrid design method of lattice structure based on failure mode显示文摘Adjusting the mechanical properties of lattice structures is important for many modern application fields. In this paper, a new design method for hybrid multi-layer lattice structures was developed to improve the mechanical properties and energy absorption, by altering and suppressing the formation of the shear band. In these hybrids, all unit cells were divided into two parts:(i) diagonal unit cells and(ii) matrix unit cells. Four categories of unit cells were selected to construct the hybrid multi-layer structures. The compressive moduli, ultimate strengths, and energy absorption properties of the laser powder bed fusion(L-PBF)fabricated structures were assessed by experiments and finite element analysis(FEA). The results revealed the great impact of diagonal unit cells on the mechanical properties of the structures. Stronger diagonal unit cells than matrix unit cells led to hybrid structures with enhanced mechanical properties. Compared with a uniform body-centered cubic(BCC) lattice structure, the relative density of the lattice structure consisting of the weakest BCC matrix unit cells and strongest BFVC diagonal unit cells(coupling of BCC, FCC, and VC) exhibited an increase of 20%. The compressive modulus and ultimate strength of this structure rose by more than 200% and 90%, respectively. Two types of structures with specific properties were generated by hybrid design.The first displayed higher modulus, superior strength, and elevated specific energy absorption(SEA) but lower crash load efficiency(CLE). The second illustrated simultaneously higher SEA and elevated CLE. The present results provide a new insight for improving the load-bearing and energy absorption capacities of lattice structures. | Chuanlei Li Junfeng Qi Panding Wang Zeang Zhao Zhe Wang Hongshuai Lei Shengyu Duan | 2022 | Science China(Physics,Mechanics & Astronomy)2022，65，9： | 0 |
| 3 | Stiffness and toughness of soft/stiff suture joints in biological composites显示文摘Biological composites can overcome the conflict between strength and toughness to achieve unprecedented mechanical properties in engineering materials.The suture joint,as a kind of heterogeneous architecture widely existing in biological tissues,is crucial to connect dissimilar components and to attain a tradeoff of all-sided functional performances.Therefore,the suture joints have attracted many researchers to theoretically investigate their mechanical response.However,most of the previous models focus on the sutural interface between two chemically similar stiff phases with(or without)a thin adhesive layer,which are under the framework of linear elasticity and small deformation.Here,a general model based on the finite deformation framework is proposed to explore the stiffness and toughness of chemically dissimilar suture joints connecting soft and stiff phases.Uniaxial tension tests are conducted to investigate the tensile response of the suture joints,and finite element simulations are implemented to explore the underlying mechanisms,considering both material nonlinearity and cohesive properties of the interface.Two failure modes are quantitively captured by our model.The stored elastic energy in the soft phase competes with the energy dissipation due to the interface debonding,which controls the transition among different failure modes.The toughness of the suture joints depends on not only the intrinsic strengths of the constituent materials and their cohesive strength,but also the interfacial geometry.This work provides the structureproperty relationships of the soft/stiff suture joints and gives a foundational guidance of mechanical design towards high-performance bioinspired composites. | Dong WU Yixing HUANG Ming LEI Zeang ZHAO Xiaogang GUO Daining FANG | 2022 | Applied Mathematics and Mechanics(English Edition)2022，43，10： | 0 |
| 4 | Adaptive enhancement design of triply periodic minimal surface lattice structure based on non-uniform stress distribution显示文摘The Schwarz primitive triply periodic minimal surface(P-type TPMS)lattice structures are widely used.However,these lattice structures have weak load-bearing capacity compared with other cellular structures.In this paper,an adaptive enhancement design method based on the non-uniform stress distribution in structures with uniform thickness is proposed to design the P-type TPMS lattice structures with higher mechanical properties.Two types of structures are designed by adjusting the adaptive thickness distribution in the TPMS.One keeps the same relative density,and the other keeps the same of non-enhanced region thickness.Compared with the uniform lattice structure,the elastic modulus for the structure with the same relative density increases by more than 17%,and the yield strength increases by more than 10.2%.Three kinds of TPMS lattice structures are fabricated by laser powder bed fusion(L-PBF)with 316L stainless steel to verify the proposed enhanced design.The manufacture-induced geometric deviation between the as-design and as-printed models is measured by micro X-ray computed tomography(μ-CT)scans.The quasi-static compression experimental results of P-type TPMS lattice structures show that the reinforced structures have stronger elastic moduli,ultimate strengths,and energy absorption capabilities than the homogeneous P-TPMS lattice structure. | Yijin ZHANG Bin LIU Fei PENG Heran JIA Zeang ZHAO Shengyu DUAN Panding WANG Hongshuai LEI | 2023 | Applied Mathematics and Mechanics(English Edition)2023，44，8： | 0 |
| 5 | Soft pneumatic actuators by digital light processing combined with injection-assisted post-curing显示文摘The soft robotics display huge advantages over their rigid counterparts when interacting with living organisms and fragile objects.As one of the most efficient actuators toward soft robotics,the soft pneumatic actuator(SPA)can produce large,complex responses with utilizing pressure as the only input source.In this work,a new approach that combines digital light processing(DLP)and injection-assisted post-curing is proposed to create SPAs that can realize different functionalities.To enable this,we develop a new class of photo-cross linked elastomers with tunable mechanical properties,good stretchability,and rapid curing speed.By carefully designing the geometry of the cavities embedded in the actuators,the resulting actuators can realize contracting,expanding,flapping,and twisting motions.In addition,we successfully fabricate a soft self-sensing bending actuator by injecting conductive liquids into the three-dimensional(3D)printed actuator,demonstrating that the present method has the potential to be used to manufacture intelligent soft robotic systems. | Qiang ZHANG Shayuan WENG Zeang ZHAO H.J.QI Daining FANG | 2021 | Applied Mathematics and Mechanics(English Edition)2021，42，2： | 0 |
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