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The Lower Extremities
Published in Melanie Franklyn, Peter Vee Sin Lee, Military Injury Biomechanics, 2017
The surrogates are considered to be biomechanical and can be reused for multiple testing with calibrations conducted when recommended. There is a second type of surrogate, which is frangible. These surrogates are meant to fracture in a manner similar as a human. Some of the initial surrogates have been used to evaluate injury from anti-personnel landmines. Simple models include the use of wooden rods to represent the bone and light concrete to represent soft tissue (Meppen Artificial Leg). Another basic frangible surrogate involves red deer tibia encased in gelatine with the dimensions of the human leg (Red Deer Lower Limb Model) (Hinsley et al. 2003). A more advanced model, the complex lower leg (CLL), was developed in Canada using synthetic materials having properties to represent bone and soft tissue of the human leg. The geometry was based on the human male although simplified to ensure consistency. The Frangible Surrogate Leg (FSL) contains even more details and was developed in Australia under the guidance of Defence Science and Technology Group (DST Group). The bone geometry was based on a cast made from 50th percentile Australian male cadaver. Synthetic materials were used to create the bones with adhesive and simulated materials used to connect them. Gelatine was then poured around the skeletal structures to form the outer dimensions of the lower leg.
Design of a Low-Cost Prosthetic Leg Using Magnetorheological Fluid
Published in Ashwani Kumar, Mangey Ram, Yogesh Kumar Singla, Advanced Materials for Biomechanical Applications, 2022
Ganapati Shastry, T. Jagadeesha, Ashish Toby, Seung-Bok Choi, Vikram G. Kamble
where θ is the knee angle and ∅ is the hip angle. Now, the next step is to find out the torque acting at the knee of the natural human leg as a function of hip angle. This torque can be taken as the torque that the MR damper is supposed to apply (by producing a suitable damping force) on the prosthetic knee. This is a highly complex task and has to be performed in steps. Step 1: Make a model of the prosthetic leg (entire assembly including the MR damper) and give inputs to its various joints as taken from the natural gait cycle to make the prosthetic leg move like a natural one. Note down the velocities and accelerations of various parts.Step 2: Make a free-body diagram (FBD) of a natural human leg and analytically calculate the torque at the knee. This will require the velocities and accelerations obtained in step 1.Step 3: Using the obtained torque, find out the required damping force.Step 4: Perform magnetic and CFD analysis on the damper to obtain the yield stress v/s current graph.Step 5: Combine the results of steps 3 and 4 to get the damping force v/s current graph.
On the impact force analysis of two-leg landing with a flexed knee
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2021
Marzieh Mojaddarasil, Mohammad Jafar Sadigh
The model moves by muscle actuators. Specifically, as shown in Figure 1(b), we developed a model of the human leg using eight muscle groups for the motion of the hip, the knee and the ankle joints in the sagittal plane including (1) Iliopsoas (IL), (2) Rectus Femoris (RF), (3) Glutei (GL), (4) Hamstrings (HAM), (5) Vasti (VAS), (6) Gastrocnemius (GAS), (7) Tibialis Anterior (TA) and (8) Soleus (SOL). Each muscle-tendon unit was modeled as a Hill-type actuator according to (Zajac 1989; Alexander 1997; Lichtwark and Wilson 2008; Arnold and Delp 2011; Millard et al. 2013; Elias et al. 2014). The Hill-type model consists of a contractile element that generates the active force according to the activation level of the muscle, a nonlinear parallel elastic element that generates the passive force, and a nonlinear series elastic element that connects the muscle into the rigid bone, representing the elasticity of the tendon. The differential equation that governs the muscle dynamics is as follows (Elias et al. 2014) where is the length of the muscle-tendon unit which can be obtained in terms of from the geometry of the model, is the length of the muscle, is the length of the tendon and is the pennation angle. Moreover, is the muscle’s mass, is the muscle's active force, which is a function of and the muscle activation level is the muscle's passive force which is a function of and finally, is the tendon's force, which is a function of the The force of the muscle-tendon unit exerted to the bones is equal to the tendon force: