---

The need for complex surfaces in CAD motivates researchers for methods which can produce smooth and visually pleasing surfaces. In this research, a new method is presented for creating compatible cross-sectional curves for surface fitting to certain sections or lofting. In this method, the distribution of sections' data points along with basis knot vectors are improved in order to reach a desired smooth surface. In compatibility process, the section curves' degrees and their knot vectors must be set equal before implementing lofting process. Based on proposed algorithm, in this research, the constructed smooth and faired surfaces can be used in many engineering applications such as reverse engineering, biomedical engineering, quality control, etc. The main focus of the method is improvement of data points' distributions and their assigned parameters in a way that by a few iterations, data points' distribution are improved in order to reach a common knot vector for all cross-sectional curves. The method is implemented on some benchmarking examples and its efficiency are confirmed. In addition, the amount of final data points' deviation from the initial section curve is analyzed using the vigorous Hausdorff method. It is worth mentioning that the quality of obtained final surface is visually pleasing. In order to quantitatively confirm that the proposed method will result in smooth and fair surfaces, MVS is used. Finally the application of the method in modeling the root joint zone of a wind turbine blade is presented.

---

Given the significance of energy absorption in various industries, light shock absorbers such as honeycomb structure under in-plane and out of plane loads are in the core of attention. In this research an analytical equation for plateau stress is represented, taking power hardening model into consideration. The equation of specific absorbed of graded honeycomb structure with the locking strain and strain energy equation is represented. The structure made from five aluminum grades is simulated in ABAQUS/CAE for elastic-perfectly plastic and power hardening model, according to the results; numerical value of absorbed energy is compared to that of analytical method. A drop weight test on a graded honeycomb structure was performed. Based on the numerical simulation results, the experimental and numerical results showed good agreement. Based on the conducted comparisons, the numerical and analytical results are more congruent for power hardening model rather than elastic-perfectly plastic one. In the first step of optimization, by applying SQP method and genetic algorithm, the ratio of structure mass to the absorbed energy is minimized. In the second step, regarding the optimum value of parameters obtained in the first step, the material property of each row is changed. According to the optimization results, while keeping the mass of structure as constant, the structure capacity of absorbing energy is increased by 18% in the first step and 264% in the second model, compared to the primary model.

---

The Assessment of strain accumulation due to nonlinear events like creep, plasticity or ratcheting phenomenon has gained importance, since it causes an increase in creep and fatigue damage of materials. Some factors like the magnitude of loading, constitutive equations or the elastic regions around the nonlinear events have effect on the rate of strain accumulation. The elastic follow-up can explain the mechanism of strain accumulation. This phenomenon may occur when a mechanical structure with elastic manner is connected to non-linear events and they are subjected to a displacement load. In these cases, the high rigidity portion of elastic region of mechanical structure may enhance the force to the regions with low rigidity. So in the local non-linear portion, the strain is accumulated. This phenomenon is proposed as an important instruction in mechanical assessment codes. In this study, the effects of Elastic Follow-up phenomenon on strain accumulation due to elastic-plastic and local creep are investigated. So the Elastic Follow-up parameter is defined by the methods which are described in high temperature assessment procedures (R5). The results revealed that the strain accumulation depends on the elastic region in structures which is described by the Elastic Follow-up phenomenon.