Papers by Keyword: Load Path

Abstract: This study presents a numerical method for optimizing the quantity and the placement of reinforcements along the principal-stress trajectories. The model representing carbon fiber composite structures consists of solids and embedded one-dimensional beam elements. Based on the Runge-Kutta method, the reinforcing structure is optimized considering the manufacturability of additive manufacturing (AM). For a case study, the optimization method is performed on an open-hole specimen. The Young’s modulus and the tensile strength of the optimized structure show an increase of more than 30 % and ~50 % in the simulation, respectively, compared to the reference specimen from another study. Robotic additive manufacturing is used to fabricate the specimen for experimental validation. The prediction of absolute values of tensile strength are reliable comparing to the experimental test, however, there is a deviation of more than 30 % in the linear-elastic behavior possibly due to the presence of voids in the printed part.

Abstract: In this work the biaxial behavior of 316 stainless steel is studied under the lens of critical plane approach. A series of ten experiments were developed on dog bone shape hollow cylindrical specimens made of type 316 stainless steel. Five different loading conditions were assessed, with (i) only axial stress, (ii) only hoop stress, (iii) proportional combination of axial and hoop stresses, (iv) non-proportional combination of axial and hoop stresses with square shape and (v) non-proportional combination of axial and hoop stresses with L-shape. The fatigue analysis is performed following four different critical plane theories, namely Wang-Brown, Fatemi-Socie, Liu I and Liu II. The efficiency of all four theories is studied in terms of the accuracy of their life predictions.

Abstract: The application of finite element method (FEM) in the area of metal forming and material processing has significantly increased in the recent years. The presented study provides details of the development of a finite element modelling approach to form a part via sheet hydroforming (SHF) process. Both FEM analysis and experimental trials were introduced in this study to produce a complex shape component from Inconel 718 material. The FEM provides a robust feasibility study for forming this part in terms of blank design, load path and process design optimisation. The simulated hydroformed part was validated by performing experimental trials. The analysis demonstrated close correlation between the predicted FE model and the physical trial.

Abstract: Based on the analysis of now available evaluation indexes to estimate the formability of Variable cross-section Y-shaped tube hydroforming, an aggregative indicator is proposed. The effect of load path on the formability of Variable cross-section Y-shaped tube is discussed by FEM simulation, and validity of the evaluation index and simulations are proved by experiment. Results show that with the broken line load path of 0-30-30-40, the value of aggregative indicator is the greatest and the formability is the best. The optional parameters are testified by experiment and the results are in agreement with the FEM simulation results.

Abstract: In this work, hydroforming of X-shape pipe connection made of copper is investigated by experiment and numerical simulation. The length of the connection branch is always a concern. The main purpose of the work is the study of the effect of the branch end boundary condition and the load path on the branch height. An elastic material (called the constraint), such as a spring, is used for controlling the branch to grow to a certain extent. It is shown that the branch end condition, if designed properly, gives rise to the considerable increase in the branch length. The increase, however, depends also on the load path which must be determined by experiment or numerical simulation.

Abstract: In this paper, the effect of load path on thickness distribution and product geometry in the tube hydroforming process is studied by finite element simulation and experimental approach. The pressure path was obtained by using finite element simulation and its validation with experiments. In simulations and experiments, low carbon stainless steel (SS316L) seamless tubes were used. The obtained results indicated that if pressure reaches to maximum faster, bulge value and thinning of the part will be more and wrinkling value will be less.

Abstract: Based on the analysis of now available evaluation indexes to estimate the formability of T-shaped tube hydroforming, an aggregative indicator is proposed. The effect of load path on the formability of T-shaped tube is discussed by FEM simulation, and validity of the evaluation index and simulations are proved by experiment. Results show that with the broken line load path of 0-35-35-60, the value of aggregative indicator is the greatest and the formability is the best. The optional parameters are testified by experiment and the results are in agreement with the FEM simulation results.

Abstract: A new index U* which represents load paths in structures was applied to a truck cab under collision. After obtaining the deformed body by a dynamic crash simulation, U* for the extracted deformed body was statically calculated. The distributions of U* were compared with the values of U** obtained in our previous report. The U* and U** distributions show almost the same pattern. However, the absolute value of U* is larger than U** by about 1.6 times. The difference is inevitable because of the difference in their definitions. The concepts of U*sum and its histogram were used to express the effectiveness of the load transfer. Using these expressions, it was shown that the main member of this cab transfers the loading effectively.

Abstract: Loading path is one of the most influential parameter in tube hydroforming(THF) process. Load history has a major effect on failures such as buckling, necking, bursting, and so on. Because loading conditions that consist of axial feeding and internal pressure are imposed simultaneously. Therefore suitable loading path should be determined to prevent onset of failures i.e. bursting on final products. This paper deals with the procedure on determination of the loading path in order to ensure the robustness of the final products after the THF. In order to verify the availability and feasibility of the proposed methodology a subframe model of engine cradle module in automotive is implemented. In this study, thinning ratio and forming limit stress diagram is used to demonstrate the improvement of the finished product. The result shows that the developed algorithm has successfully promoted the effectiveness and feasibility in the THF. Consequently, it is shown that the automatic approach on the determination of loading condition which is proposed in this paper will provide a valuable method to satisfy the increasing practical demands for designing process condition in THF.