| The impact exists in many engineering fields such as machinery,transportation,aviation,military industry,as well as our daily life.The impact force is often several times the weight of the object itself,most of which is harmful.In the engineering field,impact affects the life of working parts,reduces working accuracy and stability,endangers operation safety,and reduces production efficiency,which is a major scientific and technological problem restricting the development of national economy.During the movement of people,the impact wave generated by the contact between foot and ground can spread upward through human bones,endangering human health,such as degenerative joint disease,loosening of prosthetic joints,plantar fasciitis and stress fracture.Cushioning is an effective way to solve the impact problem.The cushion device can prolong the impact time and reduce the impact force.Although there are many types of cushion devices,there are still many shortcomings compared with biological structures with high-efficiency cushion function.Therefore,the development and design of cushion device with better cushion performance is of great significance for improving the life and efficiency of machinery,and improving the comfort of people's life and work.In recent years,the rapid development of bionics has inspired the innovative development of cushion technology.The quadruped's lower limb can adapt to a variety of complex roads and maintain excellent mobility.Its lower limb can effectively release the ground impact force and achieve safe,stable and efficient movement.Therefore,this paper takes the German Shepherd's lower limbs as the research object,according to collecting and analyzing the kinematic data of its lower limbs during the ground contact stage,reveals the ground contact cushioning strategy of the canine lower limb.Through analyzing the shape,structure and biomaterial characteristics of the metapodial pad,analyzes the cushioning mechanism of the metapodial pad.Based on the multi coupling cushion mechanism and bionics method,a bionic coupling midsole with good cushioning performance is designed and manufactured.The main contents of this paper are as follows:(1)The forelimb and hindlimb of canine have different movement patterns and cushioning strategies.By analyzing the joint angles changes and joints displacements of the limbs of canine,it was found that the forelimb did an inverted pendulum movement during the ground contact phase,and the forelimbs passively flexed through the wrist joint,stretching the muscles and ligaments around the wrist to absorb impact energy.However,the hindlimb did push movements during the ground contact stage,the hindlimb actively flex through the ankle joint,the lower limb muscle system actively contracts to absorb impact energy(2)The canine metacarpal pad and metatarsal pad have different biomechanical functions.Through comparative analysis of the peak vertical ground reaction force,the time needed to reach the peak vertical reaction force,the area of contact with the ground,the average pressure.It was found that the metacarpal pad has the function of cushioning and supporting in the movement,the metatarsal pad has the function of cushioning,but support function is not significant.(3)The material characteristics and the discrete distribution characteristics of canine metapodial pad are conducive to its cushioning function.By fitting the uniaxial tensile test results in the finite element software,the hyperelastic model and parameters of the foot pad were obtained.The viscoelastic characteristics of metapodial pad were tested using a dynamic mechanical analyzer.Based on the results of CT scans,reverse engineering modeling technology was used to reconstruct the finite element model of the forefoot in the sagittal and coronal planes and the simulation calculation was performed.The results show that the discrete distribution of the metapodial pad can make the metapodial pad fully deformed,prolong the action time,and reduce the impact force.(4)The canine metapodial pad is a cushion system composed of a two-layer cushion unit.The canine metapodial pad was systematically studied by the combination of tissue staining methods,SEM,MRI,and reverse engineering modeling techniques.The results showed that the inner cushioning unit of the metapodial pad is composed of the collagen fiber layer of the dermis and subcutaneous tissue wrapped with fat tissue;the outer layer unit of the metapodial pad is formed by the dermal papilla embedded in the honeycomb stratified epithelial tissue.The finite element simulation calculation shows that the outer layer of the metapodial pad has a cushioning effect.(5)Based on the canine leg joint motion and structure and morphological characteristics of the canine foot,this thesis proposes that the excellent cushioning function of the canine leg-foot system is the result of the coupling between the multi joint motion coupling subsystem of the canine leg and the foot coupling subsystem based on the structure and morphology.The two subsystems are the coupling elements of the dog leg-foot system.The two subsystems are coupled through the coupling modes of position.The gradual release of the impact is realized through the non-equilibrium combination which shows the overall high-efficiency cushion function.(6)The design and manufacture of the bionic coupling midsole are carried out,and the performance test is performed.According to the coupling cushion mechanism of metapodial pad,the coupling bionic cushion element is designed.Through range analysis and orthogonal polynomial regression analysis,the primary and secondary order of factors affecting the coupling bionic cushion element is determined.The coupling bionic cushion midsole is made by silicone gel complex model method,and the performance test is carried out.The results show that the bionic sole with bionic coupling buffer unit has better buffer effect,but the wearing comfort of bionic sole is related to the distribution of bionic coupling unit. |
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