A Layer-Arranged Meshless Method for the Simulation of Additive Manufacturing with Irregular Shapes.

Additive manufacturing (3D Printing) has become a promising manufacturing method as it can produce parts in a flexible and efficient way, especially for very irregular parts. However, during the printing process, the material experiences a great temperature change from the melting temperature to room temperature; this causes high thermal strains and induces distinct deformations which degrade the quality of the printed parts, especially in metal 3D printing. In order to reduce possible problems and find possible solutions, a prior evaluation by simulation is often adopted. Nevertheless, since the 3D printing process generates parts in a layer-by-layer way, the analysis model should also be layer-by-layer arranged and used with a layer-by-layer based analysis process to simulate the layer-by-layer additive printing; otherwise, the simulation may not match the real behavior. In order to meet these requirements, a new meshless method is proposed to match the situations and handle these problems. As a meshless method, the modeling is not constrained by the element distribution. In addition, the analysis model generated with the proposed method can be arranged in a layer-by-layer way and combined with the proposed layer-by-layer analysis scheme, so it can then match and simulate the printing processes. Furthermore, the layer-by-layer arranged models can be automatically created, directly based on the STL (STereo-Lithography) geometry model, which is a de facto standard in the 3D printing industry. This makes the proposed approach more straightforward and efficient. To validate the proposed method, two parts with holes inside have been printed and simulated for comparison. The results show a good agreement. In addition, a highly irregular part has also been simulated to demonstrate the effectiveness and efficiency of this proposed method.

Modeling sound transmission of human middle ear and its clinical applications using finite element analysis.

We have developed a new finite element (FE) model of human right ear, including the accurate geometry of middle ear ossicles, external ear canal, tympanic cavity, and mastoid cavity. The FE model would be suitable to study the dynamic behaviors of pathological middle ear conditions, including changes of stapedial ligament stiffness, tensor tympani ligament (TTL), and tympanic membrane (TM) stiffness and thickness. Increasing stiffness of stapedial ligament has substantial effect on stapes footplate movement, especially at low frequencies, but less effect on umbo movement. Softer TTL will result in increasing umbo and stapes footplate displacement, especially at low frequencies (f<1000Hz). When the TTL was detached, the vibration amplitude of umbo increased by 6dB at 600Hz and two peaks (300 and 600Hz) were found in the vibration amplitude of stapes footplate. Increasing the stiffness of tensor tympani resulted in a slightly decreased umbo amplitude at very low frequencies (f<500Hz) and significantly decreased displacement up to 12dB at middle frequencies (1000Hz1500Hz. As (TM) thickness was increased, the umbo displacement was reduced, especially at very low frequencies (f<600Hz). Otherwise, the stapes displacement was reduced at all frequencies.